Nothing wrong with high milers. I'd prefer a 100k car that had been looked after with regular oil changes etc than one with 60k with patchy history.
Just be wary of cars that could have their clutch on the way out, timing belt coming up etc.
Those are often the real reasons for sale (that the seller would likely keep quiet about) on cars coming up to higher miles.
Just do your homework on service intervals, how often the belt should be changed, and so on. A big wad of receipts is often a good indication of the car's history as much as the service book.
HPI it, a proper one. The cheaper text message HPIs aren't that comprehensive and you could come unstuck.
Check for rust on the front arches, underneath the rear badge/boot handle, and on the sills. The arches should be covered by VW warranty, but in practice some owners have more success in getting through the red tape and actually getting VW to agree to the repair than others.
I'm sure there's much more, and I'm sure there's a proper buying guide somewhere (if so could someone put up the link?).
Good luck, and let us know how you get on.