Travelers intrigued by the "Treasure Houses of Britain" exhibition at the National Gallery will find plenty of help available if they want to tour the homes from which the treasures have come.

A primary purpose of the museum show, at least from the British point of view, is to promote travel to Great Britain and to the hundreds of stately homes that are a part of its heritage. There's also the hope that Americans will venture to outlying areas of Britain, beyond London and the well-trod paths to Shakespeare's home in Stratford-on-Avon and the university town of Oxford.

Among the incentives to aid sightseers on a trip across the Atlantic:

*Escorted tours of a week or more to many of the homes represented in the exhibit, including the chance to enjoy lunch or dinner in some of them. Samples of the tours are described below.

*A free "Treasure Houses of Britain" road map, available from the British Tourist Authority, locating all 200 homes represented in the show, the nearest train station and suggested "first-class" accommodations nearby. For a copy, contact the BTA at 40 W. 57th St., New York, N.Y. 10019, (212) 581-4708.

*A special $23 "Open to View" ticket, good for admission to 500 homes, castles, museums, gardens and other historical buildings, including the Tower of London. It can be purchased through a travel agent before you depart for Great Britain (half-price for age 15 and under) and is valid for a month from the day it is first used.

*A "British Travel Centre" in downtown Washington offering information and brochures about visits to Great Britain and its historic homes. The "Treasure Houses" road map is also available at the center, which is open Monday through Saturday, 10 a.m. to 6 p.m., at the Old Post Office Pavilion on Pennsylvania Avenue NW. It will remain in operation through March 16, when "Treasure Houses" closes.

"The whole exhibition is one big commercial for Britain," says Bedford Pace of the British Tourist Authority office in New York, aimed at translating "the museum experience in the National Gallery into a travel experience for Britain." Last year, about 3 million sightseers toured the so-called "Magnificent Seven," considered the most frequently visited of Britain's stately homes. About a third of them were Americans.

Lest the influence of the justifiably popular museum show send you speeding immediately to Great Britain, it is important to know that most of the homes -- including five of the "Seven" -- are closed in the winter. Touring season is generally from April through October.

This means that the 200 homes that have sent objects to Washington will be able to have the treasures back in their customary settings by the time doors open again for the 1986 season.

There are a number of ways to see Britain's great homes: as part of an escorted tour from the United States; on day-long bus trips departing from London hotels; by train, using a BritRail Pass; or on a drive-yourself tour in a rental car. For the athletic, hiking and bicycling tours wander the British countryside, usually with plenty of opportunities to visit the homes and castles.

A popular way for many Americans is to find a comfortable hotel or inn outside London for a week, and then take daily sightseeing excursions by rented car from there. Michael Herbert, who oversees medieval Warwick Castle in Warwickshire, northwest of London, particularly recommends that strategy.

One reason is that it gives sightseers a chance to take in a variety of attractions in the neighborhood. (His historic castle fortress, the oldest of the "Seven," is located near Stratford-on-Avon and the beautiful Cotswold Hills.) Another is that tourists on their own can linger at the castle as long as they want.

Though many of the 680,000 visitors who show up at Warwick Castle annually arrive by day-bus from London -- the "milk run," Herbert calls it -- too often they are given only a hurried look. "It's a pity," he says. He recommends spending a leisurely four hours at Warwick, either on your own or with a guide provided at the castle. (Warwick is open daily except Christmas. Admission is about $5 for adults, half-price for children.)

Completed in 1360, Warwick remains unusually well preserved, sitting on parklike grounds (where peacocks roam) on the Avon River about 10 miles from Shakespeare's birthplace. It houses a large collection of arms and armor (for both rider and horse); a dungeon and torture chamber; and a 12-room exhibit, "A Royal Weekend Party, 1898," featuring 29 wax figures by Madame Tussaud's in Victorian dress.

Herbert would discourage anyone considering a whirlwind visit to all of the "Seven" -- they also include Castle Howard (famed as the setting for TV's "Brideshead Revisited") and Blenheim Palace (birthplace of Winston Churchill). "It's not practical," he says, "unless you're a nut. They're stretched all over the country."

Still, in any part of Britain, as the tourist office's map readily illustrates, the traveler is not very far from one of the National Gallery's Treasure Houses.

Among the escorted tours available to Britain's stately homes:

*A Taste of Britain: An escorted motorcoach tour that will take you to at least four of the "Magnificent Seven" this spring and summer is the 16-day "A Noble Journey: Castles, Manor Houses and Fine Gardens." It is one of two itineraries offered by A Taste of Britain.

Limited to 20 participants, the tours promise "a leisurely pace" and a chance to become familiar with the places visited. On the "Noble Journey" itinerary are Blenheim Palace, Warwick Castle, Castle Howard and Harewood House (another of the "Seven"), which features a four-acre exotic bird garden on the grounds.

Accommodations are in "coaching inns and manor houses," either with historic interest or a fine dining room. "Noble Journey" departures are May 10, June 7, July 12 and Aug. 9. The land price is $2,325 per person (double occupancy), including 15 nights' first-class lodging, full breakfasts outside London and 12 dinners. Air fare is extra.

For more information: A Taste of Britain, 2000 Center St., Suite 1380, Berkeley, Calif. 94704, (415) 893-5639.

*Christie's: Christie's auction house in London is scheduling a series of tours next year to several of the homes represented in the show and to homes never opened to tourists before. At some, lunch or dinner will be served.

The 10-day tours willwill depart monthly, beginning Jan. 5, through the summer of 1986. They are described as a "voyage of discovery into a way of life." Participants will visit antique markets, wine vaults, London's theater district and Christie's auction house. There also will be demonstrations on preparing the food served in the homes through the generations.

Travel in Britain is by motorcoach, and accommodations are either in luxury hotels or one of the treasure houses. No two tours are alike, since different homes are being made available each month.

The cost is about $2,100 per person (double occupancy), including room, most meals and bus transporation. Air fare is extra.

For more information: David Mitchell & Co., 200 Madison Ave., New York, N.Y. 10016, (212) 685-9871 or (800) 221-2278.

*Abercrombie & Kent: You can stay in country house hotels -- among them mansions and castles -- while touring the British countryside on one of a variety of flexible self-drive and escorted trips offered by Abercrombie & Kent, a travel firm.

A sample of a self-drive tour is "The Visiting Card," a week's excursion southwest of London to the West Country, the elegant city of Bath and the Cotswolds with time out for a visit to Blenheim Palace and Broadlands, another of the "Seven" and the former home of Lord Mountbatten. Departures throughout the year.

Near Bath, lodging is in Ston Easton Park, an 18th-century Palladian mansion surrounded by a large private park. Trout fishing and horseback riding are available.

The tour price, for lodging, breakfast and car rental, ranges from $1,064 to $1,492 per person (double occupancy), depending on the size of the car chosen. For the lower price, you get a stick-shift Ford Fiesta; for the top price, a Mercedes 230E. Air fare is extra.

For more information: Abercrombie & Kent, 1420 Kensington Rd., Suite 111, Oak Brook, Ill. 60521, (312) 954-2944.

*English Homes & Country Tours: The choice is among a handful of escorted motorcoach tours, including the two-week "Scottish Castles and Highland Heather." Groups of 20 to 25 participants visit "stately homes, castles, manor houses, gardens, cathedrals, medieval churches and historic cities and towns."

Accommodations are in the homes of the Scottish "gentry and professional classes," usually no more than six persons to a home. The idea is to give participants a chance to meet the Scottish people at home.

The price is about $1,800 per person (double occupancy), which includes rooms with private bath, all but one meal and land transportation. Air fare is extra. Departures in 1986: July 2, July 30, Aug. 13 and Aug. 20.

For more information: Ken Leahy Associates, 5342 Charmes, Sarasota, Fla. 33580, (813) 371-8383.

*American Express: A deluxe "limited edition" is what American Express calls its 16-day 1986 British Heritage motorcoach tours of "stately homes, gardens and castles."

Groups are limited to 28 participants, the pace is relaxed, and the welcome to London begins with a private, chauffeur-driven car to take you from the airport to the New Piccadilly hotel.

Among the highlights, as described in the travel company's 1986 Europe trip catalogue, are dinner at Longleat House, home of the Marquis of Bath, and a night in the Devonshire Arms, a coaching inn from the 12th century that has been restored by the Duchess of Devonshire. Among the sightseeing stops: Windsor Castle, Stonehenge, Stratford-on-Avon and Warwick Castle.

There are 12 departures from April 24 through Sept. 25. The cost is $2,595 to $2,665 per person (double occupancy), depending on the date of departure. The price includes 14 nights' accommodations and most meals. Air fare is extra.

For more information: Contact an American Express office. BOSTON'S RENOIR:

Seven of Boston's hotels are offering weekend-only packages that include tickets ($5 value each) to the Renoir retrospective at the Boston Museum of Fine Arts. The show, featuring more than 100 of the French impressionist's paintings, will continue through Jan. 5.

The packages vary in price. At the Parker House (800-THE-OMNI), the rate is $52.50 per person a night (double occupancy) with breakfast included. At the Boston Park Plaza Hotel (800-225-2008), the rate for two nights is $90.50 per person (double occupancy) with a dinner at the Cafe Rouge and parking included.

Other packages (all rates per person, double occupancy):

Copley Plaza Hotel (800-225-7654): Two nights for $87.50 with breakfast.

Copley Square Hotel (800-225-7062): Two nights for $79 with breakfast, cocktails and free parking.

The Colonnade (800-223-6800): One night for $70 with breakfast, parking and free transportation to the museum or two nights for $155 with breakfast, parking, museum transportation and a dinner at the Cafe Promenade.

The Hotel Meridien (800-223-9918): One night for $52.50, with parking and a Renoir "gift."

The Inn at Children's (617-731-4700): Two nights for $81, including a Renoir canvas tote bag and a discount for dinner at Sterling's Restaurant.

For other information: The Greater Boston Convention & Visitors Bureau, Prudential Plaza, Box 490, Boston, Mass. 02199, (617) 536-4100 or (800) 858-0200. FIRST-CLASS COMFORT:

More perks for the well-heeled traveler. Air France is installing power-controlled seats in the first-class cabins of its wide-bodied 747 fleet. The airline expects to have them in place by the end of the year. Older seats were adjusted manually.

With an effortless touch of one button in the armrest, the back of the new Air France seat gently lowers; with the touch of a second button, a leg rest rises.

When the seat is fully extended, passengers can stretch out almost (but not quite) horizontally. (First-class seats also are wider than coach-class seats, and there is considerably more leg room between rows.)

By comparison, coach-class passengers can recline only slightly in their narrow seats, a position that can become uncomfortable on long overnight flights. A first-class ticket, however, is three to four times the cost of an advance-purchase fare in coach class.

By pressing each power button again, first-class passengers are able to return their seats to a full upright position. The better to sip yet another glass of free champagne.