Not sure on all the legalities, but I do know that the U.K. recently passed a law on what types of gambling advertising you can do.
I know 888.com has certain banners that are U.K. specific and those banners can't have any wording that refers to deposit bonuses or maybe even money in general. The banners are pretty boring and just say things like "Online Poker Games" and that's it. No promotional info is allowed apparently.
Here is what 888 says in the banner section...
In light of the recent publication of the Joint Guidance of the UK Government we have prepared new advertising creative. These can be found in the libraries called "UK".
For any promotions in relation .co.uk Internet sites
you are obligated to use these creative only.
So again, not sure if the U.K. is the best choice either. Then again I'm just a dumb Yankee.
Bryan