Obviously a very high value niche.
Very nice search volume too, although the keyword is probably declining a bit:
http://www.google.com/trends/explore#q=slot machines&geo=GB&cmpt=q
There is also a slight issue in that some of the searches will be about the physical machines - this traffic has very little value compared with online gamblers.
The extension kills it for me personally - it's not worth investing time, effort and cash into a domain that has very little chance of hitting the #1 positions, and 0 chance outside of SEO - any advertising would hemorrhage traffic to the .co.uk.
Dave Merry has the .co.uk now and he knows what he's doing, I suspect that site will dominate sooner or later.
However, there are still .org.uks on page 1 of results in several gambling niches, and that is still very lucrative.
The other thing is that PPC is very expensive for this term - and the exact match might offer some benefit in terms of quality scores and therefore costs. In my experience the site matters much more than the domain, but the exact match certainly doesn't hurt. It's very tough for affiliates to make a profit on gambling PPC these days, the big brands can afford to spend more and even they often struggle.
I'd suggest mid £xxx, maybe up to top end £xxx if you find someone that has done well with .org.uks.
I can offer bottom end £xxx if you want to shift it. I'd put a single landing page on it and use it for PPC experiments.