GloucestershireGuy
I used to meet them on AdultFriendFinder (AFF) or Passion.com (which is the same site but in pink, so more girl-friendly!).
But, it's a real eye-opener doing it. And you honestly have to have your wits about you. I guess you're a man - in which case you'd probably be inundated by people looking to be paid for their services (I did sometimes wonder if I should charge....).
And I reckon, if it still exists, it will have gone further downhill by now - though I note POF etc have cleaned up their acts with regard to allowing just 'hook ups'. So maybe AFF has dirtied-down its act to enable the hook-ups, who knows?
POF, if you scroll right to the bottom, seems to have an 'adult site' option, which is presumably where they send people who just want sex. With AFF men had to pay but it was free for women, no idea if that's still the case.
You could also try a swinging site, they have hook up areas/boards.
Men had to wade through a lot of dross to find genuine women who just wanted sex. And I got a zillion messages a day and had to really weed them out.
Course, now I just want a nice guy to take me to dinner - tumbleweed....