Of course sex surveys are notoriously fallible - people are known, as a rule, to lie through their teeth about sex, and besides, only the more adventurous among us are likely to respond to such surveys, which is bound to skew the results. But, for what it's worth, the New Hite Report 2000 found that 71% of women were interested in trying lesbian sex. In fact, lesbian sex was found to be the third most popular female fantasy (after sex with a current partner, oddly, and sex with a stranger). Another survey, this time conducted by Cosmopolitan magazine, found that a third of women fantasised about ladies-only sex.

But while we may be wild enough to answer the odd sex survey, the same surveys suggest that while we might consider such adventures, we are not brave enough to act on our fantasies. What if someone found out? Or it all went horribly wrong? For most British women, going down the pub and trying to pull another woman will never be anything more than that: a fantasy.

Small surprise then, perhaps, in the age of the consumer, that a slow but steady change is taking place in the twilight world of escort agencies, which have traditionally catered only for men. Not only are some escort agencies offering a "bi-curious" service now but a new breed of women-only agencies is cropping up. "In the past year and a half it's really started taking off," says Amber Claire, who runs the internet-based escort service Bi-girls.

"We get three to four bookings a week just from women, and two thirds of those are bi-curious."

Sirens, another agency, reports that, in eight years of operation, bookings from women have gone from zero to 50% of the total, adding that it now offers a catalogue of "girls" catering exclusively to female clients.

Meanwhile, internet agencies such as DykeGirlz, Nomansland and Girlzworld, provide female escorts exclusively for women, and their websites are all big on pink fonts and female-friendly soft sell. The Girlzword website carries a polite but insistent reminder that "services are for women only - so men, don't be surprised by a refusal". Meanwhile, Nomansland, a new agency based in Brighton, further softens definitions by widening the menu, so that it's possible to book a female escort on a simple rent-a-mate basis: a companion for a straight woman's night out. "The response since we've started has been incredible," says Nomansland founder, Juliet Lamble. "Lots of girls want to work for us; we're getting positive feedback from clients and escorts and we've had mail from women in the States who want to use the service when they are here."

The logic of women paying for lesbian sex is plain enough. Find out once and for all whether it's true that only a woman can really know what another woman wants, but with complete discretion guaranteed. And the relatively uncomplicated nature of paid-for sex can, apparently, have extra resonance when two women are involved. "I get the craving to spend a bit of time with women, but I don't want the whole relationship bit," says one 25-year-old female "client". "I'm just looking for a bit of fun and it's very rare, the way women are emotionally, to find that. With an agency, it's like ringing up and placing an order for food - you can have whatever you want."

The fears surrounding the idea of pulling a female for the first time are eliminated, as are the performance-related anxieties of not knowing what to do, sexually, with a woman. As Myra Hird, a sociologist who specialises in sexuality and gender, says: "We grow up with all these myths about rules of dating on the other side, so there may be a fear of having to front up to a woman in a bar and say, 'Look, I don't know what to do.'"

Agencies catering for women are, they claim, extra-sensitive to the needs of first-timers, understanding that this category of women often requires the escort to initiate, navigate and gauge how far to take any sexual involvement.

With this in mind, women-for-women escort agencies do seem to try to cultivate an air of cosiness. "Some women escorts prefer being with other women because there isn't a power dynamic, it's genuine companionship rather than a business transaction," says Claire. There's also a conscious attempt to sell this as a service that the escort - not just the client - will enjoy. "To introduce someone to their bi-side is really special," says "Star", an 18-year-old, London-based bisexual escort. "For you to be the one who introduces them to it is a lovely thing to do, because it means so much to them. For them, it's so different, it's such a big deal; it's nice to experience all that with them."

Dr Petra Boynton, a psychologist researching the sex industry and relationships, advises caution, however. "Escorts are businesswomen in every sense," she says. "They're not going to say they hate sleeping with women if it's their job to do so."

Boynton argues that a rosy perception of these escort services buys into the myth of women automatically being nicer and less abusive then men, while, in truth, domestic violence in lesbian relationships is as prevalent as it is in gay and heterosexual ones.