I think it's more in the turn of a phrase than in the "writing in dialect". That can work, but it is hard to pull off without sounding forced or fake. I just read Bill Bryson's book In a Sunburned Country. It struck me as odd that he "sounded" British when I knew he was from Iowa, but then I found out that he was born in Iowa but had moved to the UK in his youth, lived there for about the next 20 years or so, and then moved back to the States. The result is that he writes with perfectly good English, but his phraseology sounds British, at least to me. It's a subtle thing, and probably hard to fake. So I'd suggest you read a lot of British authors to try and develop a feel for it. Or just write normally and let it drop that the character is from Britain, like DoctorWHO suggested. jon

 
~jon
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