Hi Eva.
Not sure if it is a good price - I'll have a trawl through the local motoring pages and let you know. However, you need to be sure that it has its proper Spanish documentation and a current Spanish MOT (called ITV here)
The documents are the Permiso de Circulación - white postcard size index card with car reg and name and address of registered keeper, stamped by the Jefatura de Trafico (usually a purple stamp) The other is the technical card (Tarjeta Inspección de Vehículos). This is A5 size, white flimsy card weight with the word 'espana' written small in light green all over it. The car reg no is stamped out in pin pricks. On one side it has all the car's details, very much like our UK reg documents but no name of keeper, and on the other side it has boxes for the ITV stamps. In your case there should be a stamp which is less than 4 years old (the first inspection is at 4 years, the next at 8 years and then I think it goes two- yearly and eventually annully). The ITV stamp of the Junta de Andalucia is green, don't know about others. The car should also have an ITV sticker on the windshield which should say next inspection 09.
I would not even consider buying a car which is not already Spanish registered unless the deal is REALLY EXCEPTIONAL as the hassle involved is not worth it and it costs as well, particularly as you usually need someone to do it for you who knows the ropes. If you don't register it before you get your residencia you even have to pay VAT on it.
Driving a UK registered car full time is no longer worth the risk - they are now getting very hot on this and there are many stories of cars that have been confiscated. The law says you can only keep a non-Spanish registered car here for 6 months. While your car bears a valid UK tax disc it is hard to prove that it has been here longer, but as soon as you no longer have a valid disc then you could be in trouble. Of course you can't get a UK tax disc without a UK MOT. Some people used to get voluntary Spanish ITVs and assume that they were covered, despite not paying their road fund tax either in Spain or UK, but this invalidates the insurance - no tax, technically no insurance even if you have paid for it There was a recent instance near us where someone in that position had a bad accident which resulted in the write off of the other vechicle which was VERY expensive and the result was he had to sell his house to pay the other party.
Hope this is helpful. See my recent post about insurance for a good deal on Spanish car insurance.
Good luck
Jane