Fresh from its success at Cannes and Edinburgh, it has already taken on a momentum of its own, relegated its creator to the role of a support- player in her own drama. "It's quite strange," says Ramsay. "Because in a sense it does become its own entity, separate from you, and you look at the posters on the Tube and think `Oh God, I made a film'. But I know it's not perfect. I mean, If I thought I'd made a perfect film I'd probably never make another one."
No, Ratcatcher is not perfect. At times this tale of kids running wild through impoverished Seventies Govan wears its influences a little too clearly (Ramsay admits to a fascination with both Robert Bresson and Terrence Malick). But it remains a startlingly whole and original piece of work; a film rooted in a sense of place and history which, nonetheless, sidesteps the sort of retro-chic that's become a hallmark of so many Seventies-set pictures.
"We wanted to do something that was quite timeless," Ramsay explains. "A lot of Seventies-set films are about nostalgia and it becomes really kitsch, like a fashion. So we tried not to do that. Plus kids from those kind of areas can't afford those kind of fashions - coloured flares and stuff. They just wear hand-me-downs."
We're sitting in a room at the distributor's office. It's a chill November afternoon. Ramsay is bundled in a woolly jumper and a scarf that threatens to swamp her, warming herself on a string of Marlboro Lights. Despite living in London for the past seven years, her Clyde accent comes through rich and un-tainted; a hangover from her upbringing in Maryhill where Mum worked as a cleaner and Dad was on the dole "or doing various bits and bobs of work". So cinema didn't loom large in her childhood? "No not at all," she says emphatically. "I was into hanging out on the streets with all the other kids."
Significantly, given Ratcatcher's painterly tone, Ramsay comes to cinema from a visual-arts background. After school, she went on to study photography in Glasgow then set her sights on a stint at the Royal College. She had applied to the National Film and Television School on a whim with just a portfolio of still pictures, but then she was rejected by the Royal College ("I totally messed up my interview") and accepted by the NFTS. "I think it might have been to do with positive discrimination," she muses. "They may just have been getting a few women in as camera people."
It proved to be an awkward baptism. Ramsay was not enamoured of the NFTS's base out in the commuter town of Beaconsfield ("the Village of the Damned" as she calls it). Then she was told by one tutor that she'd never make it in the industry because she was a woman and too weak to carry a camera. Added to all this was the knowledge that she had somehow landed at Britain's premiere film school without knowing anything about film. "I hated it," she says. "I went from feeling quite confident as a photographer to feeling less than a zero."
On the positive side, the place provided her with a belated education. "I got into Bresson and Fellini and Maya Deren, and Fassbinder, and I felt really cheated actually. Why was it that I didn't get to see these films before? You go to the multiplex and pay pounds 8 and all you come away with is the feeling that someone's shat in your head." Then there was the small matter of her 10-minute graduation film, Small Deaths, which won the Prix du Jury at Cannes and effectively paved the way for her current success.
So, Ramsay emerges from this haphazard apprenticeship as something of a rarity in British cinema; a working-class Scots woman in an industry still largely dominated by middle-class Londoners. Inevitably, much is being made of this. At this year's Edinburgh Festival, Ratcatcher was hailed as the first Scottish opening-night picture since Bill Forsyth's Comfort and Joy in 1984, and the first by a woman since The Piano debuted there in 1993.
The one problem is that Ramsay's having none of it. She dismisses the Scots woman film-maker label as "marginalised, and very condescending. It angers me, actually, because I'd like people to see me as a a film- maker first. Everything else is bollocks. I don't want to start talking about my femininity or wave the tartan flag."
The same goes for attempts to pigeonhole her work. "I wish I'd never mentioned Bresson. I'm not trying to make a homage or a pastiche like all those Tarantino copycats, those film boys who are just making wank. I don't want to be obsessed by politics or social-realism, which is really limiting. It's a lazy eye that sees a film like that."
I confess that the social-realist angle had struck me; that Ratcatcher's use of a non-professional adolescent in the lead role raised memories of Ken Loach's Kes. Ramsay draws wearily on her fag. "Loach is a really good film-maker but I'm a very different film-maker so I'd rather that comparison stops now, thank-you very much." She laughs. "I'm sure he would as well."
Next up for Ramsay is an adaptation of Alan Warner's novel Morvern Callar, which she is currently scripting. After that she's planning to write and direct a film, one of a series of five, for the independent American company Good Machine. "They're low-budget features around a common theme. Hal Hartley's doing one, and Gaspar Noe." What's the theme? "Mature films about sex," Ramsay says, and then her face scrunches up in an embarrassed schoolkid's grimace.
In a way it's heartening. Because Ramsay is clearly moving on - from Glasgow, from Beaconsfield, from the pressures of following up an acclaimed debut. And yet those years spent "hanging out on the streets with all the other kids" are not so easy to shake off. There's still a lot of Maryhill in her.
`Ratcatcher' is released on 12 Nov