Follow up

Following up on my last post, an official organisation (for my market) that I contacted seem to think there's 21,000 people (at least) in the UK that I could consider to be my target market. That's a better number than I had estimated :-)
Given that the population in the US is 5 times that of the UK, even if I discount the fact that the game's theme is way more popular in the US, that gives me a US estimate of 100,000. For a sellout I'm now looking at a 0.83% hit on the estimated available market which is gooood :-)