I am here to visit Ally, which is a shop, design studio and installation space showcasing contemporary British furniture, photography, jewellery and ceramics behind its stark, clean, contemporary facade.
Ally's owner and creator, the 33-year-old graphic designer Susanna Cook, both lives and works here in the street. "I used to work in Covent Carden, but I prefer it here," she says. She is wearing high-fashion black and has a halo of Pre-Raphaelite hair. "It's off-centre. People can't get their head round what I do, and they're intrigued by it. And this is that type of area. I love it here more and more."
One can quite understand why people have some difficulty understanding the entity which is Ally. Inside the rambling, three-floored building which is the workplace, Cook runs an installation space in the basement, her graphic-design studio in a large open-plan space on the first floor (her clients include Boots and the ultra-hip Soho bar Lab), and in between, on the ground floor, the shop, which sells "everything I would like to own myself".
Susanna's flat is just down the street, and at first glance it appears to be nothing like the efficient minimalist whiteness of the building where she works. A year or so ago, when she found the flat, it was - in that doom-laden phrase beloved of estate agents - "in need of some updating". It was very Seventies: not Wallpaper Seventies, or James Bond revivalist chic Seventies, but Wendy Craig taste-bypass Seventies, with its tan bathroom suite.
But the flat had in its favour good natural light and "manageability". "Ally is a big thing to run," says the woman who, to save time, buys coffee from the cafe down the road and, back at home, decants it into pristine white cups. "This was a little space, totally controllable. I was getting divorced, moving from a flat in Camden and a house in Suffolk. This is my sanctuary."
Today Susanna's "sanctuary" might have taken as its theme the title of Matisse's famous work Luxe, Calme et Volupte, so chic and harmonious is its design. In fact, Cook insists she drew her inspiration from a rather more prosaic source, a box of artist's pastels, which she brings out to show me. "I love the colours, but I find them too messy to work with." Still unused, the decorous spectrum , inching from buff to violet, is exactly mirrored in the neat circle of four rooms.
Despite - or perhaps because of - its small scale, the flat is unusually luxurious. The first things one notices are the carpets: thick and a velvety seal-grey colour, they contrast with the austerity of so much contemporary flooring. "I've done floorboards," says Cook emphatically. "When I came here I just wanted comfort."
In small spaces, expensive tastes can be indulged even if one has only a fairly small budget. So the bathroom - whose walls are the natural chalky cream colour of plaster - is floored in polished limestone; and the bathroom lightcord ends in an elegant teardrop of sterling silver (designed by Susanna's sister Julia, and sold at Ally).
Cook limits her extravagances carefully. The kitchen units are from IKEA - "because I can't afford Baulthaup" - but she has upgraded them, so that there are granite work surfaces and brushed stainless steel surrounds.
It is this attention to detail that is one of the defining characteristics of luxury. Details such as the tiny antique bone knobs from India on the door of the drawing-room cupboard which introduce a note of dignity and tradition to an otherwise contemporary interior.
One of the great attractions the flat had for Cook was its light. When you've climbed three steep, dark flights, you open the door and receive a bright flash. To the east can be seen the skyline of the city. In Cook's west-facing, pale mulberry bedroom, the light is filtered through the leaves of the huge plane trees outside.
"I love greenery. That was another of the flat's main attractions. Next year's project is to do the roof terrace." In the meantime, Cook makes regular Sunday trips to the weekly flower market at Columbia Road to find roses in the exactly the right shade of deep crimson to complement the bedroom walls and the newly purchased flower painting by one of Cook's star artists, Lorry Eason.
If its airiness and its restrained hues contribute to the flat's sense of calme, its volupte arises from the luxuriousness of the furnishings and fittings. The sensuously curved French wooden bed, for example, with its finely laundered white linen sheets, or the exaggerated depth of the bathroom sink, or the lavish velvety upholstery of the deep sofa in the drawing-room.
All this calm, luxury and voluptuousness would all be a bit much if it weren't for the personality of the owner herself. Even when at home, Susanna Cook is a pragmatic, energetic urbanite with a purposefulness and robust sense of humour that could never have been shared by some languorous Fauve odalisque. She was happy to see the flat's small size as a challenge rather than a constraint. "I've always lived in high-ceilinged places until now, so I had to think of ways to counteract the size."
The methods she used are those fundamentals of her trade - line and vista. She cleverly employed horizontal surfaces - such as a thin line of slate shelving which now runs beneath the drawing-room fireplace - to draw attention away from the room's restricted height, emphasising its breadth. In the kitchen she has packed in storage room that would satisfy a Michelin chef. "I think they were slightly surprised at IKEA," she says. "They're not used to people who know precisely what they want."
The great strength of British design is that it doesn't take itself too seriously, and, true to type, Cook appreciates quirkiness. Her bedside table comes from a junk shop in Kentish Town and was originally used to furnish a Sixties luxury hotel. The stylishly-shaded light which seems to stand upon it is, in fact, bolted down.
She also has a genuine passion about the artists whose work she has on show both at Ally and at home. Scattered in profusion around the flat are a series of abstracts by Ross Abrahams, an artist whom she discovered when on honeymoon in Majorca. "He was quite elderly so I bought loads. I got into a sudden panic that I'd never come back." Other works gracing her walls and furniture include a photograph by Liz Rideal, a leafy tapestry by Emma Jo Webster and a gilded lamp by Charlotte Packe.
It's these highly individual touches that give this small flat a very large and expansive personality. It seems fitting that Cook should point out a card that stands on one of the bookshelves. It quotes a line of Gertrude Stein: "I wish that I was where I am."