Since this is specifically poker and casino focused, the Brick and Mortar forum may be a better place to ask.
In particular, London comes up often there. As Henry pointed out, you do need to become a member for London card rooms, but that is possible when you arrive at the casino. Bring your passport.
Here are a couple recent threads that will have some info for you.
Amsterdam Poker
poker rooms in London?
Looking for a casino in Barcelona
This one does not have as much good info, but you can try bumping it -
Cardrooms in Italy? (Venice, Florence, Rome)