Hi. I have not done as you enquire but I did register an English car in France ( a modified 1973 Range Rover ). It was a problem to start with but I found ( from the Living France website ) that it was possible to go down a Collectors vehicle route which cut through the hassle. My point is that there is probably an expats website for Spain ( try Angloinfo ) where you can either search for the info or post a question. Good luck with this.
