Terence Conran is a king-sized man shaped very much like a big contemporary sofa, of the High Comfortable Period. His presence and physique are so overwhelming that he would shock a Louis XIV chair back to Louis XIII.

The 45-year-old British millionaire talked the other day as he sprawled on a generously scaled piece of the merchandise in Conran's, the new pick-up-and-go home furnishings store in New York, just opened in the dazzling Citicorp Center complex of offices and shops. With its steeply slanted (one way) roof, Citicorp is the world's seventh largest building.

Besides Conran, the owner of 34 stores called "Habitat" in Europe, there is Conran, the best-selling author, whose "The Kitchen Book" was published to coincide with the store's opening. And there is Conran, the restaurateur.

"The Kitchen Book" - 700 color photographs - is already selling almost as fast as the Cuisinart. The first time stay-at-home Americans learned there was a Conran was when visitors to England came back home with copies of his "The House Book." It quickly became a cult, chiefly because of the thousands of delectable photographs delineating a seductive style of living based on the eight Cs: contemporary concepts, copious collections, cozy comfort and constant conviviality.

"Oddly enough, I'd tried to get an American publisher from the beginning, but they looked at the manuscript and said, 'It's too European' - until people kept arriving on every plane with it, and Fabrications here in New York sold 2,000 books immediately. So far, 138,000 have been sold over here."

Conran wrote, if that's the term, "The House Book," in the same way he runs his stores. He is, as he says, "the design czar." Five other people worked with him on the book. "The book started out as a training manual for our staff, sort of a massive catalog. We'd published before - leaflets, calendars, catalogs (they're well thought of in England). So we knew about photgraphy and drawings. But as the whole thing dragged out to two years, we realized we had put a pile of money into it, what with pictures and other graphics, and our staff time. So we negotiated a contract with a publisher and got back some, but not all, of the money we'd put into it."

After "The Kitchen Book," guess what he's working on. You got it - "The Bedroom and Bath Book." "We had to get sex in. It is, after all, a vital component." After that, the front steps book? The garage book? "No," says Conran, but you never can tell.

"The Kitchen Book," (published by Crown Publishers) is a Conran natural. "It seems strange to me," he said, "that for years we've had all those cook-books, but very little really about the design of kitchens. It was easy to do, easier than "The House Book." We began in January and finished April 15. But then, we knew the subject well."

Conran has been in kitchens a long time. He is well-known for his appetites - for everything (three wives, four houses, five children), including quantities of pasta and wine. At lunch in New York, he chose the generous sausage platter in a cafe near the Citicorp.

"I run a restaurant in London now as a hobby (Neal Street Restaurant in Covent Garden). But when I first got out of design school (London's Central School of Arts and Crafts), I wanted to make furniture, but I hadn't any money. Back in those days, there were no lively restaurants for young people in London. So I set out to open one - I'd always been interested in food. I worked for two months as a washer-up in a Paris restaurant (two-stars) to find out how a restaurant operated. Then I started something called the Soup Kitchen, based on cheap stock.

"We had an enormoos caldron full of soupstock as well as apple flan, cheddar bread and espresso, then considered wicked and exciting. The soup kitchen was in what had been a shop - we did it very plainly with pine boards and cabinets. It cost us less than $1,000. And before long we had a chain of five or six. I sold out, made $10,000 profit, which I used to build up a furniture factory."

Conran's wife now is Caroline Conran, "cookery editor" on The Sunday Times of London and the author of a great number of books. "The Kitchen Book" is dedicated to "Caroline, the best cook I know."

"She's always testing recipes so she's pleased when I do a supper," he said, answering the question of whether they fight over the facilities. "Often we work together in the kitchen. That doesn't always work out unless you ar used to each other. I, for instance, clean up as I go along."

The Conrans have done several kitchens together, including the one in his London office, described and pitured in detail in the new book. The family has almost as many houses as Conran's has chairs. Their London house, in Regency Park, a landmark leased from the government, is currently occupied by his eldest sons, who operate a motorcycle repair shop and a punk rock clothes factory there.

"The house stands in a good section to town. But the other end of its street is rather tough. My sons give the street address to their tough friends, the Regency Park to mine. All of that punk rock is degrading and depressing to me, but what I did at that age was, I'm sure, the same to my parents."

The Conrans - including three younger children - have homes in Belgium, France (overlooking the Dordogne River) and, after spending the summer in the United States while putting together the new Citicorp shop, they are thinking about buying over here. In the meantime, their principal residence is a country house 60 miles from London in the Berkshires bought three years ago. The estate is estimated to be worth at least half a million dollars.

"The house and the other buildings were totally derelict, and the 18 acres were badly overgrown. But we have enjoyed putting it to rights. I can't think why I'm not now in my office in the old stable building."

The floors were good, the brick was fine, but he had to put in new plumbing, a new roof, windows and a heating system - no small trick for a mansion of 32 rooms. "They're always full of guests. We often have 16 for lunch."

Also feeding on the premises are a number of chickens, geese and pigs.

The house isn't that old by British standards. It was built in 1972 with 1882 Victorian additons. "We've pulled down much of the later work," he said. But he hasn't made a restoration of it. For instance he has thrown three rooms together to make a salon 28 feet by 90 feet. Some purists would be horrified that he has lowered the 15-foot ceiling to nine feet. "In fact, Caroline was horrified at the idea (of the lowered ceiling), but she like it once it was done. It looks rather logical, because the ceiling now comes to the top of the windows."

Their 35-by-50-foot kitchen once was the assembly room when the house was a school. When it was a grand country house, the kitchen was the billiard room. The Conrans made it the kitchen because it was close to the vegetable garden and it had fireplaces at each end. His instructions on how to make a larder (a cool-room) like his as described in the book sound wonderful - but would only work in the cool summers of England. Still, it reads as though it's the ultimate kitchen, with great numbers of open shelves, a marvelous Swedish oil stove with four ovens that stays warm all the time, a built-in eye-level charcoal grill, auxiliary electric cooking units, solid teak work surfaces, including the drain-board.

The great oak table seating 12 or so has a changing supply of second-hand rush chairs, pitched out when they give out ("they are often worm-eaten and therefore break under the weight of heavy diners.") The kitchen equipment includes a canary and a variety of cats. Below it all are great root, wine and beer cellars. The beer cellar even has a raised floor for the barrels and a drain.

The more formal furnishings in other rooms are largely Conran designs, mixed in with antiques, an eclecticism he approves. He designed the rehabilitation of the house himself, a procedure he urges on everyone. "We don't offer a decorating service in our stores - except, of course, for commercial clients. I think it's rather sad that anyone should choose the way some other person's home looks."

Conran's may look strangely familiar to Washingtonians, as though it were one of the family that included The Design Store, Scan, Bon Marche and the Door Store, with Hechinger's as a cousin. In about a year, if things go well in New York, Conran's plans to come to Washington, probably to Georgetown. "If the portents are right."

If Conran's is new to the New World, it's been around since 1964 in London, purveying a particular sort of taste in furniture and homewares, a third of the furniture designed by Conran and staff.Conran doesn't think it's at all an especially English taste. "My hero has always been the American author, architect and furniture designer George Nelson."

There are 34 Conran's - called Habitat stores - in Belgium, France and Scotland, as well as other parts of Britain. Recently he spent two days in Russia, talking to the governmental design commissar.

Speaking of the American market in a speech to his staff at a store in France, he said, "There is also amongst young people a feeling of discontent with the very traditional approach to furnishings of their parents, and a look that they call 'Lifestyle' and we would call 'Habitat' is beginning to emerge. American Lifestyle look is very much based on Habitat, as they (American retailers) will generously admit, and you see almost as many Habitat catalogs in buyers' hands at trade shows (in America) as you do in Europe. So this seemed the perfect time to launch our stores in the USA. We hope to expand rapidly, initially building a chain of approximately 20 stores on the northeast coast."

The great strength of Conran's is that it all looks as though it had been selected by one rather strong-minded person. "All" includes sofas, vivid geometric comforters and sheets (no kingsize; the largest size in England is, appropriately, queen-size), glassware, kitchen gadgets and cabinets, pottery, window shades, dhurri rugs, handsome Indian upholstery fabric, coat hooks, Twinnings Darjeeling tea, knockoffs of Bauhaus furniture and some rather poorly made American case goods he hopes to improve upon.

"I do think that the strength of the store is the cohesiveness. It all goes through the funnel and comes together at the end. Most stores try to do too much, the Gatling-gun approach.

"I think that in the 1970s there is an end to nostalgia in home furnishings. And no one believes any longer that bad reproduction furniture confers status."

The last-minute decision (because of copyright problems) to change the name from Habitat to Conran's in the New York store created a great mess in the last few days before the store opened about a month ago. Staff dashed about, cutting off the labels on the sheets and furniture, sending catalogs, advertisings, even the "Hello, I'm So-and-So" tags for the press opening out to be re-done at the last minute - all at a cost of at least $25,000.

Conran said the American Habitat, a lighting company, wanted $2 million for their rights to the name, so he decided to go with a name he could get cheaper - his own. He probably owes Habitat something for having pushed him into using his own name - better known in America than his European stores' rather trite name.