Pick a little Brit?

Does anyone have time to Brit-pick a fic of mine? It's a Sherlock/Doctor Who/Firefly crossover fic--you don't need to know anything about the various canons, just be able to help me out with UK/British carnival terminology: for instance, should I say "carnival" or "fair?"

You don't have to worry about SPAG or anything else, I just want to make it seem vaguely plausible this story could take place in England!

Please and thanks yous. :D