Inside the Bridal Boutique at the G Street Remnant Shop, an enchanted room of white and cream laces, satins, pearls and veils, Marshene Berry wrapped herself in lengths of white French lace and smiled into a full-length, antique mirror.

"They have the prettiest and oddest fabrics here," the bride-to-be said. "You can come in here with a picture from a book and find the material to match the picture."

Berry is among the last of the brides who will be enthralled by the Victorian ambiance of the shop because the store, a fixture in downtown Washington for nearly 50 years, is moving to Bethesda in August.

The departure will leave downtown shoppers without a store that has a variety of materials, zippers, threads, ribbons and other sewing notions.

The G Street Remnant Shop, in the ornate Old Central Building at 805 G St. NW, has built its reputation by offering a sewing emporium that includes everything from everyday cottons to hard-to-find leathers and furs.

"We need more space," store manager Molly O'Sullivan explained. "Also, our lease came due and we couldn't negotiate a long-term arrangement. We want to grow. We don't want to be limited by time and space. But because G Street is an institution, we don't take this move frivolously."

"The Bridal Boutique will be twice its present size at the new location," bridal consultant Linda Winner said. "Right now, we have lace in storage because we have no place to put it."

Customers spend hours browsing and poking through the store's three floors that brim with bolts of material, from inexpensive polyesters to vicu na (South American goat) wool that sells for $400 a yard.

There also are arrays of beads, buttons, ribbons and metallic fabrics. Many of the laces and buckles are displayed in antique china cabinets. Framed antique lace collars and old buttons hang on the walls. Wicker baskets of buttons or silk sit on counters.

On the seventh floor, customers find designer silks, Guatemalan cottons and genuine wax batiks. There also is the Silk Boutique, a small sitting room with an antique sofa and a roomful of fine silks, feather boas and more metallics.

Customer reaction to the move is divided.

"I'll find them. I'll drive wherever they go," said Berry, who was selecting material for her gown and those of her 12 bridesmaids.

Shopper Mary Campbell said, "I'll take one Saturday each month and go to Rockville."

But some customers who rely on public transportation said they will have difficulty visiting the new shop, which will be near the White Flint shopping mall, across from the White Flint Metrorail station scheduled to open in late 1984.

"I don't have a car. I can zip over here on the Metro," said Margery Thompson, a customer for 20 years. "Do you know how famous this place is?" she asked. "People come from New York to visit this place."

Janet Urban, a Justice Department lawyer and a lunch-time shopper, said, "When shopping here becomes an effort, I'll probably go other places."

In addition to the loss of convenience, several customers said they will miss the store's turn-of-the century charm that many believe will be hard to replicate.

"Coming here is quite an adventure," said Helen Rivera, who was visiting the bridal boutique for the first time to search for heavy, sequined fabric for the wedding gown that her grandmother will make using a Diana Ross pattern.

"I was told it was quite a place, and everything I was told is true," she said as she walked past a mirror with a white, feathered boa draped around her neck.

Aundra McCoy, a Woodward & Lothrop buyer's clerk and a jewelry designer, said, "Going to G Street Remnant is like walking through a museum. There's no other place downtown where you can get such good fabrics."

Woodward & Lothrop and Hecht's department stores have phased out their once-large sewing departments, and Garfinckel's does not sell sewing goods. The Button Shop, 725 11th St. NW, offers sewing notions but no fabrics other than lining materials.

"It's just here lately that I can talk about the move," said Dorothy Lancaster, a sales assistant at the G Street Remnant Shop for 19 years. "This is like home. I've been here long enough to see some of the customers get old and retire, see their children grow up and now see their grandchildren come in. They tell me change is good. I hope they're right."