TERENCE CONRAN, who wrote "The House Book," "The Kitchen Book," and, of course, "The Bedroom and Bath Book," has been accused of single handedly taking the stuffiness out of furniture.

It's certainly an exaggerated claim, because other people have contributed heavily to the general trend toward casual living -- what's sometimes called the Turtleneck Approach to interior design. lConran, through his books and his chain of some 50 stores in New York, England and France, has gone a long way towards establishing a look that is both comfortable and well-designed.

The Conran concept is based on functional forms, fattened out with a flip of fantasy. Looking at Conran himself, who's been described as resembling a comfortable overstuffed sofa, you can see he is a man of not only taste but appetites. And his stores and books promote such desires.

Now Conran is coming to Georgetwon in a monsteer two-story 35,000-square-foot-plus store, handsomely ensconsed in a 101-year-old former hay warehouse. The address is 3227 Grace Street, but as all Georgetowners know, to call Grace a street is an exaggeration. The easier way is to say it's behind the hold in the ground that's behind the Rive Gauche.

Conran's opens to the public on Friday.

The great arched glass windows of Conran's overlook the C&O Canal. A pleasant garden is designed to show off Conran's garden furniture while allowing people to rest a bit while shopping. The top floor will hold furniture, much of it devoted to designs made by Conran's own team, according to Kim Dominique Agnew, the marketing manager.

The lower floor will sell bed linens, stationery items, lighting (including some hot selling spot-light units), and a vast array of kitchen utensils. Cooking is close to Conran's heart. He and his wife Caroline Conran, "cookery editor" of The Sunday Times of London are currently finishing up "The Cook Book." Conran's store catalogue has recipes along with furniture specifications.

The interior design of Conran's is by its own firm, Conran Associates.

Conran's occupies the south side of a hugh multi-million dollar edifice being constructed by Western Developers, to the interesting design of architects Alan Lockman & Associates. Below Conran's are two levels of parking. Above are 35 duplex townhouse condominiums with fireplaces and 19-foot-high vaulted ceilings under the handsome copper roof. The units are to be sold this summer.

Eventually, according to Courtney Lord, who is Western Development's vice president of leasing, Georgetown Park (as the area is called) will contain three levels of 120 stores (including a Garfinckel's), more townhouse condominiums, and several levels of parking. A glassed-in pedestrian walkway will lead across the canal to M Street.

Conran's is expected to compete here with the long established Scan stores, The Design Store, the Door Store, and to some extent Hechinger's. Conran's claims to have a wide selection of merchandise, even to the extent of offering to do "House Paks" -- rooms in a box? -- which include everything from linens, furniture, curtains and rugs to wallpaper, hardware and notepaper. fThese House Paks are shipped to your new address, in Georgetown or Hong Kong. Conran's also has started carry Welsh antiques, which is a departure for the contemporary-minded firm, according to Serine Hastings, merchandising manager.

The arrival of Conran's on the Canal shows once again, that Washington with its wealth of fine old houses, has entered the 20th century where furnishing them is concerned. CAPTION:

Illustration, Conran's new store will be in Georgetown Park's Canal House. Western Development Corporation