Not much being honest,
the main one would be the chelsea casino I thnk, thats if there is a casino in chelsea.
The regional casino ones there would have to be obviously some casinos for you too advertise.
You would obviously need to rely on banner ads and sign ups for the casinos.
I dont think that regional casino would be a widely searched term.
Your on a sticky wicket from my point of view, regarding the traffic going to these websites and would be a very low turnover.
You might be better off trying to set up a basic website, putting some adverts and seeing if you can get some traffic for them.
I have loads of domain names for gambling websites, a lot do not have anything on them as yet but the casino or betting business is a very hard thing too get into.
Butttttttt if you can get into it and have a successful website then its worth the rewards.
Hope this helps
Regards
Mark