I know what you mean (well... sort of... we don't have the whole "cheek kissy" thing in America). I, for example, really just don't like to be touched. It just bothers me. People are filthy.
However, I don't think it's rude to tell people that flat-out, even if it's like... the first time I've met them or something. Just don't be a dick about it. A simple "Eh! Don't like to be touched!" (or in this case, kissed) in a friendly and humorous matter has always done the trick for me.
Then again, you may have waited to long to take that approach, so meh.