When is Skepticon coming to the UK?
Don't know for sure. You'd probably have to check with the organizers. I know that one of the main people behind it is JT Eberhard. You could ask him (although I don't know whether he'd have time to respond).
My guess would be that it won't be for a while. Skepticon is one of the younger conventions in the atheist/skepticism movement and will probably need to make a "name" for itself in the states before it can consider becoming an international event.