You don't know how much money the taxi drivers have put into keeping them running though - ultimately any car can go onto 500k miles with enough investment. Most don't because of age.
All cars are a roll of the dice especially at this money. The 1.9 is often heralded around here as the embodiment of reliability bit of course those can go wrong too. There are a few people on the skoda forums with 1.9s which have launched a piston through the side of the block. There are also people with the (totally unreliable if you read too much ocuk) 2.0 at 200k+ with no serious issues. The 1.9 is more robust it seems but the polar viewpoints of the 2 engines is deeply skewed.
If it was me... I'd probably get a £500 Peugeot 406. Nice and comfy and they seem to never die, even if you want them to. The old TD can run on chip fat too. If it breaks just throw it in the bin for £200 scrap and buy another. Plenty around for £500 with low 100s on them but there are lots of mega mile examples around (
http://www.autotrader.co.uk/classified/advert/201510017422480)