Buzzfeed has published 'The 17 Best Ways To Annoy A British Person'. Examples include:
5. Actually take the last biscuit when they ask you if you want it.
8. Violate the sanctity of a queue.
17. Ask them if they’re Australian.
There's more at the link. As a British-colonial expat, I can assure you that most of them will work! Note to self - I must make sure Miss D. and Oleg don't see that article . . .