Best free site to place to find local U21 via the internet?

Im a 20 yr old guy who has thought i was gay for years. now im feeling bicurious and want to experience with a girl. For ease however, I'd rather it'd be with a stranger until I know whether this is just curiousity or not. I was wondering what good free websites there were, either chat rooms or personals to find girls in london. I dont want to have to pay though, as I know some personal sites are free to join but then cost to use all the good features