Dinner at the Twits and Mr and Mrs Twit's Upside Down Cocktail Cavern can be found at:
The Vaults (Leake Street entrance)
Directions to Leake Street Entrance
To get to The Vaults, exit Waterloo station via Exit 1, next to Platform 1. Turn right out of Exit 1. Continue straight for 100m until you come to a set of stairs, walk down the stairs and turn right onto Leake Street, the graffiti tunnel. The Vaults will then be visible on your right hand side.