Only a sample size of one, but I never saw a more excited fan than the guy I was sitting next to at the Bills game last year in London. He was wearing a Manning jersey (half the stadium was wearing gear from one of the other 30 teams) and came by himself, wasn't really rooting for either team but loved the game. He said he'd been to several NFL games. It seemed to me that the Brits were pretty into it, as of course were the Americans.