I know I have really wasted my time on these posts, as when buying cars people seldom take the advice of a professional and prefer to listen to mates etc. They go out with all the good intentions of checking everything, seldom go through with it and wonder later why the thing does not work as it should.
The other thing to think about is a £600 car is it is like a £25 bike, go for something a little odd and you can have many years of good service, try and by a fashion item and it will be scrap.
Those sporting Fiats looked after will be worth £1500 in 5 years time, write this down or keep a copy, that is the opinion of the trade any way. Where as a mk1 Corsa that will depend on the price of scrap at the time.