Many sites in London, but none like TAG.
Adultwork, Punternet, Punterlink, Acemassage are a few coming to mind.. The google more specifics, like. for instance, "soho walkups" "London Chinese Massage parlours" and more options will pop ut. London has a lot of variety, but one needs to know, and a lot of homework is equired. Not like here, where more or less everything is done by others on TAG!!