Firstly I would not recommend doing a lot of miles in a £625 car. These kinds of cars are not reliable.
Secondly, could you not save up a bit more money? A £1500 car would be infinitely better than a £600 one.
the only thing that would put me off one would be if you where carting kids etc about as small cars of that age aren't too safe when for example a small car of new age hits them