Where AE and BE differ, Brits will recognise 99% of the AE variants, due to our consumption of US films and TV. I suspect the percentage in reverse is a bit lower. However, in a globalised age perhaps the division is a lot less relevant than it used to be. For example, within the United Kingdom, there's now virtually no debate about the relative merits of English English v. Scottish English or Bristol English v. Newcastle English, although the amount of difference in both cases is comparable to AE v. BE, excepting the spelling. It's just assumed that you speak the one you happen to speak, but are pretty much up to speed with the others, give or take the occasional specific term. We're just not arsed/don't give a monkey's/can't be fecked with the differences.
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