[Riflema]

Possibly the best medium-to-harsh swear terms: bugger it! and bollocks! The latter can be pronounced "bollo" (after an old joke about gateaux).

[Fast Moving Angel]

One of the funniest outtakes I've ever seen was of the show House M.D., where Chase (an Australian) flubbed a line and exclaimed, "Oh, bollocks!!!"

That said, the Britishisms that bug me the most are "pins" (referring to a woman's legs), "heavily pregnant" and "fell pregnant". Come on, how do you "fall" pregnant? (insert smart@$$ comments here) And what if you're only 2-3 months along? It's not "heavy" yet, unless you're carrying an elephant or something. Sheesh.