The creeping Americanism thing does wind me up (no surprise as part of my job is translating American marketing information into English marketing information, and that involves a surprising number of changes).
The 'fill out' this always wound me up - we 'fill in' as we are writing in the empty boxes requiring our information, I suppose.
But what MAKES ME SO IRRITATED is:
...person arrives at counter at coffee shop. "Can I get..." ARGH! NO NO NO! "May I have..." or if you think that sounds a bit OTT "Can I have"... .