I can't see any good reason for thinking that vanchi is not authentic. Of course, all this may be a bit of a joke (education of vanchi in the subtleties of Mancunian humour perhaps?) which I'm not getting. Anyway, what would be the point of a Utd or Liverpool fan coming on here to... well, what? Don't want to lay on the flattery too thick (always a danger that I'll be thought to be another part of a Cunning Plan to undermine something) but there is always the matter of intelligence to put into the mix.
It is the time of year when not much is happening so digression is always on the cards - was it on this thread that people wandered off the argue about the correct pronunciation of Vimto? All good stuff.