There is one main reason why they are so cheap.... The head gaskets blow on them approximately every 30 thousand miles, I suggest if you buy one that you get a pressure test done. Obviously look for the milky residue under the oil cap and check that the heater works (also a sign if it doesnt). At a garage you are looking at about £500 to fix this.
Other than what I have already mentioned the electrics are shocking on them, they have a habit of the airbag light coming on due to crap connections under the drivers seat and generally they are quite thirsty.

Honest opinion is to steer clear, I had a friend buy one, he kept it 7 months and had to spend over £1500 in repairs. The car seemed fine when it was bought.
Cats go on them quite frequently as well.