Hi Mike,
for what its worth I think your prospective buy is slightly over the odds, remember that if it's not been done, at 120,000 a cambelt change is going to be due. At 140,000 new set of platinum spark plugs 6X £12 plus labour. Have a look on autotrader.co.uk there are loads under 3 grand. don't worry about high milage, go for the newest you can afford. At 3 grand everything should work, there should be no rust anywhere, the interior should be pristine. Listen for grinding ball joints when on full lock, juddering brakes - wrongly tightened lugnuts bend the rotors, take it on a dual carageway and brake hard from speed.
It's a truly great car the MKI but don't pay too much!
Good luck.