lucy24 - 9:47 pm on Aug 11, 2011 (gmt 0)

Write the way you're comfortable-- but ask an American to look at the text to make sure there's nothing they genuinely don't understand. Generally that would apply only to lexical differences. "Bespoke suits" is probably OK because the word simply doesn't exist in American. And there are some Britishisms like "lift" and "lorry" that all Americans know. (Or know incorrectly, like "public school".) But a phrase like "return ticket" risks serious misunderstanding. ("How can I return if I haven't even gone there yet?")