My advice if coming to Spain would be to keep the RAV4 and put it on Spanish plates.
The Rav4 is a good reliable car!! Good cars in Spain are expensive especially reliable Japanese cars.
Driving a RHD 4*4 is not a problem because you are higher than the average car. The only hassle is car parks and having to stretch across for the ticket.
Putting it on Spanish plates will cost about EUR800 and that includes changing headlights and road tax.
It would cost less if the British Consulate did not charge its nationals so much for the Baja Consular document. I believe they charge 7 times more than other Consulates but you pay for their jolly in Spain becuase they don't offer much in the way of help otherwise!