David - There is a group called the Anglo American Shooting Society(AASS) who regularly travel back and forth between the US and the UK with some spectacular guns (at least the ones I saw at Bray's Island a few years ago).
This article mentions several British members of the AASS. If you could find a way to contact one of them, they could give you the procedure for moving guns
http://theshootingsociety.com/blog/1...game-fair.html