As Tadd said its good advice to buy Spanish.
To add further to his post if you take a UK registered car to your holiday home, and it's in your name, it has to be fully road legal as if it was still being driven in the UK but on Spanish roads, bit of a hassle when MOT time comes around as well....Forget any advice you will get that when your UK MOT is due you can book it in the UK , while in Spain, and drive home to have it done.
On here are plenty of horror stories of ex-pats driving UK cars around, get stopped by the cops, have a missing document or two, been noted that the car is always in Spain, UK plates, etc etc, only to have the car taken away.
I am sure you have noticed that used cars in Spain are a lot more expensive in Spain as like for like then the UK, while new cars do seem to be a better deal then the UK one's.