Do you use British slang or spelling?
Are you in fact British, or from a part of another English-speaking country where this slang/spelling is used commonly?
Does it bother you when people who are not British/from another place where it is used commonly use British slang/spelling?
I do not, because it does bother me when people do. But I do say that things are brilliant sometimes when I mean that they are awesome. I don't think that is really something that the English own, per se.