There are a handful of places near The City that offer extras, but this usually involves spending a lot of money in the VIP areas and works out more expensive then seeing a WG. I have certainly seen and had plenty of extra fun in Venus (Farringdon), and also seen things happening in Spearmint rhino. But not something you can just ask for in your first visit, better if you already know the girls and waiters etc, and definitely helps if everyone is up for "partying".