WHEN WHAT YOU WANT most at night is a pair of flannel pajamas, it's time to get away for a romantic weekend. Pennsylvania and Maryland abound with elegant old homes that offer bed-and-breakfast getaways, often for no more than the price of a run-of-the-mill motel room. But what motel offers a real water mill, heirloom furniture, a warm country kitchen brimming with good food and history, and vistas of rolling farmland or forest? Here's a sampling of relatively nearby country houses where you and yours can rekindle a flame or just enjoy being alone, together. The timing's perfect, with Valentine's Day around the corner. So forget the Godiva and go for a drive, with a romantic destination in mind. MILLBRIDGE

Even if you didn't spoon to the tune of "Down by the Old Mill Stream," true romantics will appreciate the route to this hideaway: Across a stone bridge and up a winding drive past an old stone mill to a 200-year-old stone farmhouse, atop a hill on 12 rolling acres in Chester Springs, Pennsylvania.

Once a self-contained mill community, the buildings still standing include a carriage house, barn and stone well just like the ones on country postcards, and a 15-room armhouse that combines rustic charm with the best of modern renovation. To achieve their goal of a home with beautiful views from every room, the owners added floor-to-ceiling windows on all sides.

Open the old farmhouse door and enter a hallway bright with sunlight. A dramatic circular staircase and mahogany floors shipped from Panama add to the feeling of light and warmth. The house is a pleasing mixture of textures and styles, furnished with Oriental rugs, early American rough pine furniture, smoothly polished English antiques and contemporary pieces.

Couples will appreciate the living room with its huge stone firepace and, in summer, the sun porch that looks out to the garden and pool beyond.

Both guest bedrooms, each with private bath, are furnished comfortably with contemporary pieces. The "Maple Room," whose twin beds can be pushed together, has windows on three sides. From the "Orchard Room," with a single bed, guests can see the pear, apple and cherry trees outside.

A full country breakfast is served in front of a fire in the panelled library brightened by Palladian windows, or, in warm weather, by the pool. After breakfast, stroll through the 12 acres of grounds; perhaps you'll catch a glimpse of the deer that come down the hill behind the pool at dusk. When there's enough snow, guests sled down the hill out front, and then warm themselves in front of the cozy library fire.

For the really adventurous, Millbridge also offers "Flights of Fancy" weekends year round, depending on wind conditions. These French-theme country escapes include two nightslodging and two full breakfasts and, the piece de resistance, a dawn or dusk hot-air balloon ride over Chester County, complete with a chaser car and a champagne toast. You'll also partake of a French pique-nique, tour a nearby winery and dine by candlelight at a local French restaurant -- for $395 for two. Now that's a heaven-sent Valentine.

Millbridge -- Near Chester Springs, Pennsylvania. For specific directions and reservations, call Bed and Breakfast of Philadelphia 215/688-1633. Accommodations: one single and one double room, each with private bath. Includes full breakfast. Outdoor pool. Winter sledding. Rates: Couple $45, single $40. Open year round. Features "Flights of Fancy Weekend." No children; resident cat who lives inside, and dog who stays outside. WHITETHORN

Whitethorn, in the heart of Pennsylvania horse country, is the picture of country repose, with a split-rail fence galloping along the country lane that leads to this early 18th-century farmhouse.

The three-story, 15-room house stands on the remaining 10 acres of an original 1,000-acre Penn land grant, along with a barn, apple orchard, trellised grape arbor and a 150-year-old boxwood. In 1715 a gentleman farmer built the house using the wood cut from the oak and cherry trees on the property. The house grew in size along with the family in the early 1800s but many of the early details remain, including a den door studded with nails (a contemporary status symbol) and the original locks and hardware.

The dining room, built in the 1700s, contains old winding stairs and the original door and wainscoting. The fireplace in the large Williamsburg-blue living room is decorated with its original blue-and-gold fleur de lis tile, and the summer kitchen, built in 1836, has its original oak paneling.

There are only two guest rooms on the second floor (one's a single) and they share a bath. For trysters, the blue room boasts a fine view of the old trees outside and a double, fourposter canopy bed with an antique crocheted bedspread.

At Whitethorn guests enjoy simple pleasures: The brick wrap-around porch, with wrought iron railing and rockers, surrounded by 300-year-old sycamores and ginkos invites just sitting. And in the spring, it's front row center for the show provided by the owner's championship race horse working out in the dressage ring next to the house.

More energetic types can take a quiet walk along trails on the property to see the numerous songbirds and owls, or visit the nature preserve that borders Whitethorn's land on three sides.

During hunting season, you may be awakened by the horns of one of the three fox hunts that regularly ride through the property. Guests may bring their own horses to be boarded, or the owners can arrange for horseback rides over the gently rolling farmland. When winter's over, the back country roads provide excellent bicycle riding as well.

And sometimes, at the end of a summer's day, the owner bring a 20th-century pasttime to this 300-year-old setting: They set up a stereo on the brick patio, put on the big band songs of the '30s and '40s, turn up the volume, and invite guests to dance with them under the stars.

Whitethorn -- Five miles from West Chester; 21/2 miles from Unionville. For reservations and directions, contact Bed and Breakfast of Philadelphia, 215/688-1633. Accommodations: One single and one double room with shared bath. Television sitting room. Rates: single $30, double $40. Stalls for boarding horses. Children with sleeping bags welcome; horseback riding can be arranged. A featured guest house on Bed and Breakfast of Philadelphia's "Flights of Fancy" balloon weekend, $395 per couple. Nearby: Longwood Gardens, two miles; Chadds Ford four miles; quarter mile from Brandywine River canoeing and tubing. MALVERN COLONIAL

Venerable boxwood hedges border this 15-room Pennsylvania- stone farmhouse near Malvern. As you walk up the flagstone path to a long, white pillared front overlooking acres of fields, you feel as if you've gone back to the 18th century.

After returning from England two years ago, the owners bought this house, intent upon restoring it and turning it into an English-style bed and breakfast. Under the red shag carpet, they discovered the original random-width oak floors with hand-hewn nails. The house, built for a gentleman farmer in 1690, was added to in 1750, and sprouted a third floor in 1780.

But the original summer kitchen, built in 1690, conveys much of the colonial charm and history of the house. And guests get to enjoy a full country breakfast there.

The copper sheeting down the center of the kitchen door was intended to stop the flaming bows and arrows of the Indians. And note the hand-forged metal hinges, the original oak beams in the ceiling and the ladder to the loft where the children of the early owners slept. Under the window is an old stone sink with a drainage hole to the outside, said to be one of only two such pre-1700 sinks in Pennsylvania.

In fall and winter, there's a roaring fire in the walk-in fireplace that has its original swing crane. Carved in the nearly 300-year-old mantel you can see the initials "W.F. 1812." The oak armoire, carved oak sideboard with beveled mirror and wooden rocker add to the charm.

The owners have furnished the rest of the house with a mixture of 19th-century and contemporary pieces. The living room with original Delft Victorian tiles around the fireplace is filled with antiques collected on travels in England, including leaded- glass bookcases and an old gramophone with a recording of Queen Victoria's coronation.

Guests have the entire third floor, which has two guest rooms, to themselves. Guests of the same party may reserve rooms together, so the spacious third floor can become a private two-room suite with two televisions.

Ask for the Victorian room with the white, iron double bed in which the owner's grandfather was bor This large room, sparsely but comfortably furnished, opens to a large bath with a grand view. The oversized ball and claw Victorian tub is perfect for two.

The surrounding four acres have both history and fish. The tunnel that leads from the "keep," a cold storage shed, was built to allow the owners to escape from a British attack during the Revolutionary war. Later on, the tunnel and keep became a part of the underground railroad for slaves escaping to the North. Guests may fish in the meandering old mill stream.

For a rendezvous, walk up the path of old railroad ties to the large pool surrounded by trellises of rose bushes. The towering evergreen trees which provide a natural border make this a perfect setting for summer skinny dipping. And at night, the underwater lights add just enough to the moonlight to make this an ideal trysting spot.

Malvern Colonial -- Near Malvern off U.S. 202, 10 minutes from Exit 24 of the Pennsylvania Turnpike. For reservations and directions contact Bed and reakfast of Philadelphia, 215/688-1633. Accommodations: Two rooms, which can be used as a suite by a family. Shared bath. Television and air conditioning. One room has twin beds; the other, a double bed. Single $30, double $40, family of four $75. Includes full breakfast. Has pool and stream. Open year round. Children over eight welcome, as are small pets. Ask first about pets. Resident dog. French spoken, as well as Spanish and German. Nearby: five-minute drive to Valley Forge Park and Music Theater; 30 miles to antique stores of Adamstown; and 30 minutes to Philadelphia. LONGSWAMP BED & BREAKFAST

Longswamp, near Mertztown, Pennsylvania, takes you by surprise. After miles of country roads dotted with unassuming farmhouses and small clusters of grocery stores and country gas stations, the first sight of this stately three-story, Federal- style white stucco mansion is arresting. Standing at a village crossroads, Longswamp seems like a sentry from a more elegant era.

From the garden, you enter the enclosed hallway that connects the main house to the oldest part, a 1740 summer kitchen with welcoming fireplace and original pine floors.

The spacious main house, with its wide center hall and oversized rooms, was originally built as a large farmhouse around 1740. Colonel Trexler, a country gentleman, in 1860 built the living room and added the mansard roof to enlarge the third floor, creating the imposing structure that befitted his station.

Legend has it that when the colonel discovered his unmarried daughter having an affair, he shot her lover. Because of the colonel's rank and community standing, he escaped jail or hanging. But the colonel suffered, and after his death, his ghost could be seen standing at the window of his room, watching the road. In 1905, his concerned neighbors arranged a successful exorcism in which his spirit was taken to a nearby mountaintop and sentenced to sweep clean forever a small ring of land.

Guestsy stay in the colonel's second-floor room with its white four poster bed, private bath and original pegged wood floors. The second-floor verandah, with its hanging begonias and comforable wooden rockers in summer provides a perfect place to read or lounge.

On the third floor, four more guest rooms share two baths. Plants, floral wallpaper, country bureaus with lace runners and beautiful woven scatter rugs, handmade by the owner's friend, add to the welcome as do the complimentary wine, cheese and crackers left in each guest room.

Reading and lounging are respected activities. Each double bed has two excellent reading lamps and four pillows. Extra quilts and blankets are within easy reach, and bathrooms are kept stocked with extra shampoo, conditioner and other necessities so easily forgotten.

Elsa Dimick, the owner and a professional caterer, serves lots of homemade food, including jams, jellies and bread. Enjoy a hearty weekend breakfast of orangce, fresh fruit, waffles or french toast, bacon or ham and coffee cake in front of a roaring fire in the summer kitchen in winter, or on the patio in warm weather.

You can stroll the five-acre property, take a gentle hike on the adjacent 40 acres, play full-court basketball in the barn, or borrow bicycles for a leisurely ride on country roads. Nearby is Blair Creek Inn, a restaurant Elsa recommends for dinner. Then stroll back slowly, sit in the garden, and gaze quietly at the stars in a country sky.

Longswamp -- RD 2, Box 26, Mertztown, Pennsylvania 19539. 215/682-6197. Call for directions. Accommodations: four double rooms sharing two baths, and one double room with private bath. Continental weekday breakfast; full country breakfast on weekends. Rates: $55 plus 6% tax for a double; $45 plus 6% tax for a single. Open year round. Reservations: Call Elsa Dimick, 215/682-6197, or call Joyce Stevenson of Bed and Breakfast of Southeast Pennsylvania, 215/845-3526. Children over eight years acceped, free if staying in same room with parents. Credit cards not accepted. No smoking allowed in the bedrooms. No pets. Nearby: The clothing outlets of Reading and the antique centers of Kutztown and Adamstown. Horseback riding locally and skiing at nearby Doe Mountain. GLENBURN

Guests approach this imposing 27-room Georgian mansion near Taneytown, Maryland, by crossing a small bridge over a trout stream, and winding up a drive flanked by towering black walnut, willow, maple and oak trees. The house, with its wide expanse of lawn and stately pillars, is pure country gentry.

Glenburn was built around 1840, originally part of a 4,000- acre grant. From 1842 to 1890 it was a private boarding school for boys, from which the home takes its name.

The house, which has appeared on the Maryland House and Garden Tour, is elegantly furnished with antiques. Enjoy complete privacy in the 1853 Victorian addition originally built to house the extra school boys. This part of the house has its own living room with fireplace and television, dining room and an inviting wrap-around porch with wooden rockers.

That porch attracted the present owner's mother to the house. While her husband was searching for a house in the country, she turned down each possibility, saying: "When it has a porch that turns the corner, then I'll be interested." Ever since 1937 when she saw that porch, the home has been in the same family.

The porch provides guests a good vantage point from which to watch the deer, pheasants and rabbits that come down to the creek in the morning. Guests are invited to fish for trout in season.

The three bedrooms upstairs, two of which connect, share a bath and are furnished with Victorian furniture. All rooms are air conditioned. The bedroom with the double cherry-spool bed connects to both a private dressing room and a private screened porch with wicker furniture and a swing.

Victorian beds and bureaus furnish the other two double bedrooms, which can connect to accommodate families. The view from the windows is of sweeping lawn and the creek.

Continental breakfast is taken in the guest dining room or on the porch or the back lawn in good weather. Since Glenburn is a 463-acre working farm, the owners can suggest pastoral places for picnics and walks. Permission is needed so that no one inadvertently disturbs the farm machinery or encounters the bull.

Glenburn -- Taneytown, Maryland. Directions, telephone and reservations are available through Sharp-Adams Bed and Breakfast Registry, 301/261-2233. Accommodations: Three double rooms, one with private dressing room and enclosed porch. Shared bath. Rates: $48 single or double for room with screened porch; $35 other rooms. Includes continental breakfast. Open in the spring ("Right before the daffodils," says the owner), summer and fall through Thanksgiving. Children are welcome and the fee varies with the accommodations. No pets. Nearby: Glenburn is 13 miles from Gettysburg, near the Catoctin mountains, the Carroll County Farm Museum in Westminster and the antique shops of New Market and Taneytown. GREAT OAK MANOR

F. Scott Fitzgerald wrote of country houses such as this one. From its walled garden bordered by hundred-year-old boxwood and its circular drive on the land side, to its magnificent view of the Chesapeake and private beach on the water side, this country estate provides the appropriate setting for a life of privilege and a weekend of romance.

Great Oak, a 25-room, Georgian Revival manor house near Chestertown, Maryland, was built in 1938 by Russell D'Oench, an heir to the W.R. Grace shipping fortune. The scale of the house is arresting, and the fine details exemplary. From the land side, you enter a great hall with a magnificent spiral staircase to the right. Sunlight streams in from the doorway at the end of the long hall that leads to the wide expanse of lawn bordering the bay.

There are nine bathrooms, nine fireplaces, a music room, gun room, library, dining room, servants' hall, sun porch, potting room and many bedrooms.

Both Great Oak's size and fine craftsmanship gained it the Maryland Society of Architects Award for excellence in 1940. Carvings over the entranceways to rooms signal each room's use. Books of Homer and Virgil announce the library; a crab and shellfish declare the dining room. The gun cases in the gunroom have leaded glass doors, and a handpainted map of the Eastern Shore on a wooden roll pulls up to reveal the bar, which occupies the space beneath the spiral staircase.

The house, a combination of antiques and contemporary pieces, has an ambiance of privileged elegance. The music room contains a Louis XVI loveseat and an Italian marble-top console table. The library mixes English Hepplewhite, French antiques and Persian rugs.

Each of the four double guest rooms, furnished comfortably with contemporary pieces, has a private bath. Three of the guest rooms have water views and fireplaces. One room has a sitting room. And tucked away in the laundry room is a '50s juke box complete with vintage rock'n'roll selections. A supply of quarters is kept handy.

Commanding views accompany elegant living. From the terrace on the water side of the house, enjoy a sweeping view of the Chesapeake. Watch the sunset over the bay from the hammock, or follow the path to the thousand-foot private beach with excellent swimming in summer.

Or you can visit Great Oak Landing, a resort nearby. For a charge (depending on the activity) guests may use the tennis courts, swimming pool, nine-hole golf course, marina and play miniature golf. Guests who arrive by boat will be driven to the manor house.

Great Oak Manor -- Near Chestertown, Maryland. Directions: Provided after reservations are confirmed. For reservations and directions call Dick Simns, 301/778-5796 or Sharp- Adams, the Maryland bed and breakfast registry. Write Great Oak Manor, RD 2, Box 766, Chestertown, Md. 21620. Accommodations: two-room suite; three other double rooms. All rooms have private bath. Many have fireplaces. Three have water views. Includes continental breakfast. Rates: The two- room suite, $145 a night per couple, two-night minimum on weekends; Sunday to Thursday, $125. Extra people in suite $15. Other rooms $95 a night on weekends, with two-night minimum; $75 a night Sunday to Thursday. Open mid-March through January. Reservations required. No walk-ins accepted. No charge for children, but children are accepted at manager's discretion. Nearby: Great Oak Manor is seven miles west of Chestertown, on the Eastern shore of Maryland.