bigdoggie-
I split my time between London and New York,
I don't think you'll find anything particularly like that in London itself, there are some places on the outskirts.
However I would try Les Girls in London (just do an internet search) or The Cottage where I think the only girl worth visiting is Emma and is definitely recommended given it won't set you out more than 60 or 80 quid, also just do an internet search for the cottage
There are a couple other "houses" one in Kensington - but the name escapes me.
Also, the most valuable resource you'll have while out there is a review board called punternet - again just do an internet search as I don't know the rules about posting actual websites, but punternet is a collection of "field reports" which will really help you out...
if you can, go up to Manchester for a weekend, its the "punting" capital of the UK and though it strikes me as odd for a cold northern location in England it has an amazing amount of "spas" and i think would be just what you're looking for - if you do make it try World Famous Babes, Sandy's or... can't remember the last one but there are 4-5 at minimum and all have websites.
happy punting,
let me know if you have any other questions.
/cb