Just as an FYI, nothing wrong with them being import GTIs...they have a better spec (sunroof etc), only downside is no alarm but that's easily rectifiable.
Certainly nothing that would cause anyone to walk away from one if it's an otherwise good car... 
True but I think the issue is paying 07-plate money for what's really an 05-plate which was sat around for a couple of years not doing anything. Also lack of alarm could affect insurance I would have thought.
Couple of threads from 8 years ago commenting about them:
http://www.golfgtiforum.co.uk/index.php?topic=58818.0
http://www.tyresmoke.net/forum/topic/91218-new-here-buying-gti-import-need-help/
Yes, but as so often with cars, plenty of vehicles may well be 2005/2006 but actually on 2006/2007/2008 registration.
I have seen 55 Plate Bora (MK4s) before.........
TBH on the old threads you linked it's just people speculating... "high temperatures perishes all the rubbers"... lol
When it comes to buying a car for ~£6k I don't care where it comes from as long as it's tidy and specced as I want
The imported ones all came with a 2 year VW warranty. Still covered by manufacturer recalls. componently it's exactly the same just has an originating stamp in another country.
hoo har over nothing. it's a better specced car for the same (or less) money. i think they all came with leccy sunroof, IMO i prefer the earlier MK5s as they have no roof aerial so a cleaner look (just personal preference!)
alarm can be an issue but as i said, easily rectifiable. mine was never a worry
