Chip has said it all really, i went to test drive a mint working bora 150tdi last year, it drove like shit when i planted my foot. the owner claimed it needed EGR sorting which would be about £100, if it was that i'd have had a bargain, but so easily could have been a number of other things too.
on the other hand i bought my tt xr2 for cheap as it had a fault he thought was gearbox or clutch, i had spares so bought it, got it home and turned out to be clutch pedal ratchet and an engine mount, £10 later all was good.
moral of the story, if it's not right then pay spares or repairs money.
its tough out there with old cars, you can pump thousands in to see a return of only a few quid, MOT tester may not give a shit to be honest, i know some i have been too are too obsessed with how much work is done to it, they forget the basics which i point out afterwards if i thought it was borderline.
just get it sorted and enjoy it, it's not the end of the world afterall.