Barcelona is best for car supersites. Madrid 2nd best. The further south you go in Spain the more the used car trade falls into the hands of horse traders who protect their significant profit margins jealously and with the aid of local government. You cannot buy at auction in Spain unless you are a trader. Not in Sevilla, anyway. There were some expat English car dealers operating in the Javea-Calpe area, but I can’t vouch for them. It’s worth getting hold of "Motoring in Spain” THIRD EDITION (ISBN No. 978-84-611-9278-6), by Brian J Deller. More at www.spainvia.com/motoringinspain.htm