I’m not sure you have any case really. Firstly, is Games and Casino a legally registered trademark in the US? Is it also registered in the UK?
If it isn’t, I don’t see how you can claim anything – just because you have Games and Casino in the US shouldn’t preclude someone creating a company/domain of that name in the UK, doubly so given how generic it is.
It’s highly likely that this domain was created in bad faith, but what if it hadn’t have been? What if this UK guy just had the same idea for a site as you did? Surely you wouldn’t expect to have a right to the domain then.
In fact, imagine it the other way around. Imagine there was a UK company, established 1996, called Games and Casino, and they suddenly discovered the web and were going to sue you! I think then you would be glad that a company in one country can’t just grab the domains of other countries.
I realise of course that in this case there is bad faith, and he is almost certainly just trying to trade off your name. But that really doesn’t matter. Unless you have that trademark registered in the UK, you have no right to the domain name at all.
As for incurring him costs, that’s just not going to happen. Unless he’s a complete idiot he’ll just ignore your lawyers. His costs will be £0 and yours will be $000s, and he’ll just keep ignoring you. Chances are you’ll give up before he does, and even if you don’t, what has he got to lose? He paid £10 for the domain, and the worst that is at all likely to happen is that you’d be granted the domain (but that wouldnt happen, as above). You’re certainly not going to get costs. No court is going to issue damages worth thousands or tens of thousands in damages against some small time chancer with no previous court history.
I think you’re letting your anger cloud your judgement on this one. You should have registered the domain in the first place, and at this point you have vastly more to lose than you do to gain. In all probability he’ll fail to sell the domain at anything like that price, and perhaps you can even grab it yourself for a reasonable price.