Years ago, I used to pay an entrance fee at Sun and Steam (Steam and Sun?) near Euston. You could sit in the lounge and chat to the girls for as long as you liked, before and after.
I think it was £15 to go in, and then 30 mins with the girl was £40, (may have been £50). Good value, lots of girls to choose from, but if you just wanted to look, it cost you £15. Fair enough.
No idea what it's like now, or if it's still there