There are the Strip pubs like Browns at Shoreditch and various others which are free entry. The girls are very attractive and get down to nude with legs spread in one song on the public stage 6 times an hour, you have to contribute £1 in a pint glass to each girl that performs. They will ask if you want a one song private dance in the room at the rear (and possibly now on tables in the main room since the recent re-fit) for £10-15, no hard sell and quite nice chatting to the girls as they come round. If you do go back there, there is no touching, no extras, unless there is something private you can arrange for when the girl finishes her shift, but I doubt it, unless you are George Clooney's better looking brother. OK for an hour or so to watch the pretty girls and have a normal priced drink, maybe a private dance with the one you fancy most and you could get away with spending less than £30, then book an escort, incall or outcall, for afterwards to release the pent-up tension.http://browns-shoreditch.co.uk/
It's going to be very difficult, if not impossible, to get the entertainment part of a Strip Club along with the sex of a Brothel in London, you probably need to got to places like Holland, Germany, Prague where the laws are more relaxed for that. The licensing authorities and the management here are pretty hot on selling sex on the premises, they won't want to risk getting closed down when they're making too much money from mugs watching the nude titillation and paying for entry fees and overpriced drinks. I have caught wind of reports of places that do offer both, but since this is illegal they do get found out and shut down, you would probably have to get an invite from a known regular.
If you want guaranteed sex in a party (but not stripshow) setting, maybe a sex party like Lady Marmalade's would be best.http://www.ladymarmaladeparties.com/hostesses