This, it turns out, is something of an understatement. From the crazy- paving on the floor and the spider plants sprouting from hanging baskets to the disco ball dangling from the ceiling and the trash-glam clothes, Readman has taken from that era and made it her sweet, and highly idiosyncratic, own.
Ruffled florals, crochet knits in brightest gold, suede shirts, and fringing here, there and everywhere all hark back to that decade. This means, of course, that Joie (pronounced Jo-eeey - the shop is named after its owner) looks set to take its place on the fashion map in the course of the coming season.
It may seem as if there's always some sort of Seventies revival going on somewhere in fashion (and Fifties, Sixties and more recently Eighties revivals, for that matter), but, like it or not, the Seventies are about to take off again in an almighty way. The likes of Gucci, Versace, Dolce & Gabbana and, well, just about any other trend-inspired designer worth his or her salt, have once again plundered what many still regard as the most unashamedly riotous of decades - in style terms at least. Come autumn, once the high street has picked up on the new styles, we'll all be doing it.
Those who just can't wait that long might like to know that, while designer garments are likely to cost hundreds, even thousands of pounds, at Joie's nothing costs more than pounds 300 - and that's for a hand-made wedding dress crafted out of old denim jackets, or anything else that happens to take a customer's fancy.
"People can get a really nice top here for pounds 35," says the designer. "They can buy a dress for pounds 65. I don't want my clothes to be expensive. I want people to be able to wear them. I'd like to think that even if I did get big, my prices would still be kept really low. Now is our Jane Fonda moment, by the way." Joie picks a different icon each season and then dresses the mannequins - and indeed, the entire shop - in heartfelt tribute. "We've already done Mia Farrow. Next season is Kate Bush `Babushka'..."
Because of its location - hidden away in a backstreet sandwiched between Holborn and the British Museum - not many people know about Joie just yet. A handful of the British fashion capital's more exuberant stylists swear by the place. Otherwise, its proprietor says, Joie mostly tends to attract "Swedish tourists with blue hair".
And Joie is, of course, more than happy to oblige them. Her shop is quite definitely not the sort of place where anyone would be turned away. "I don't mind people coming in and not buying anything," she says, "and I'm always happy to open after hours. I don't want to frighten people off, or to be seen as `fashiony'. If someone's excited, I'll make anything for anyone."
Well, perhaps not quite anyone. When Joie first opened her doors to the public, she had the bright and characteristically kooky idea of covering the floor with black lacy knickers, spaced evenly like a wallpaper pattern, under sheets of Perspex. Her collection was equally racy, consisting of PVC dresses and baby-doll nighties - all intended to be worn in a knowing and ironic kind of a way, of course.
Rather than attracting the sort of swinging, fashion-forward clientele she had anticipated, however, the shop was suddenly flooded with gentlemen of a certain age who tended to wander in off the street and rifle self- consciously through the rails in hope of finding something a tad saucy that they could take home for the missus.
"They thought it was a sex shop," the designer confirms, not even remotely fazed by what might seem a catastrophically unfashionable turn of events. But then Joie Readman is no ordinary designer.
Now 30, she grew up on a working farm near Epping Forest (hardly fashion central) with her mother, father and two younger brothers. "There were cows in the way when we went to school," she says. From an Ursuline convent school near her home, she went on to study fine art at Goldsmiths, completing her degree in 1992, when the college was at its most heavingly fashionable.
"I was always into fashion, though," she insists. "I used to crimp my hair and wear tight jeans and lacy shirts to barn dances." She must have cut quite a dash. "Actually, everyone just used to laugh at me," she says. Or, in the case of a more savage breed of provincial disco dolly, simply clocked her one: facial glitter, Joie informs me, was not tolerated then.
By the time Joie left college, her love of "dressing up", her singular style and her eye for the screamingly kitsch and quietly subversive was entirely of the moment, and people stopped laughing. She had wardrobes full of clothes, and friends queuing up to borrow them.
In serious need of money, she turned this to her own gain, taking Polaroids of the said friends in complete outfits, and then packing everything - from hair accessories to shoes - into a see-through Perspex box with the snapshot stuck to the top so that punters would know just what they were buying. Named Pandora's Box, it sold like hot cakes from Bond in Newburgh Street - then the centre of the British fashion universe - at pounds 35 a pop.
Joie went on to design coquettish, barely-there dresses in fondant colours, frisky knits covered in pompoms, Calamity Jane gingham picture hats, marabou bras and knickers and, in an urban-cowgirl moment, fluffy pink chaps, selling through Nineties high-camp fashion mecca, Sign of the Times. Her work appeared in Elle, i-D, Vogue and, well, Playboy at the time.
"I'm mad about glamour," she says, changing her trusty French sheepdog Coco's red chiffon scarf to a green one. "When people come here, they can buy something original, something they can wear to a club where no one else will be wearing it. I want everything to be dripping with glamour."
From jewelled hairpins to fluffy mules, and from lacy tops imported from Thailand to flippy, flower-strewn skirts, Joie's stock is indeed a sight for even the most fashion-weary eyes.
Joie, 10 Museum Street, London WC1 (0171-497 5650)