09 Dec 2009 17:28:
I had my UK registered left hand drive car re registered here in Spain last November and can comment as follows:
I gave the job to someone who specialises in car registrations importation etc and all he required was a copy of the escritura, NIE, and the UK documentation for the car. First the car was ITV'd and then he handled the rest of the transfer work. I did not have to pay any importation or registration taxes as the car was registered to me for more then the previous 6 months so the only cost I incurred was for the ITV traffico charges and the agents commission in total around €800.
The transfer took about a week to do and the car was in my possession the whole time the agent took care of the ITV appointment, transfer new number plates and also made sure the IVTM (road tax) was paid in the costs. When I was looking to do this I contacted a number of agents all of whom were giving me varying information some stating that I would liable to the importation / matriculation tax even though the car was in my name for more then 6 months due to recent changes in the law etc.
So from my experience unless you speak to someone who really knows what they are doing you may end up forking out more then you need to!
Incidentally I originally imported this car from Germany to the UK and handled all the importation transfer myself and it cost around £600 including £400 for the road tax!
Thread: new law about buying a car in spain