A year or so ago, the BBC website published a rather silly article, where they invited readers to write in with the Americanisms which annoyed them most. The BBC published these without any comment, causing a bit of a stir in the (mostly American) linguistics blogosphere. In fact it turned out that many of these 'pet peeves' that people sent in weren't even Americanisms at all, and of the five examples the journalist had opened the article with, only one hadn't started life in Britain.
Perhaps in an attempt to redress the balance slightly, the BBC have recently published an article about Britishisms (also known as Briticisms) that have been creeping into use in North America, and invited American readers to send in examples of Britishisms they had noticed being used. Thirty of these were then published in a follow-up article, with definitions from Oxford English and Collins dictionaries.
Note - a lot of these words are informal or colloquial, and one is downright rude (in the sexual sense), or as one dictionary has it - 'vulgar', and another 'taboo, slang'. But none of them are particularly nasty. Try your hand at using them with four short exercises.