I presume you mean driving from the UK. I got the ferry from Portsmouth to Bilbao and drove down to Jerez last Jan. Took about 10 hours to drive through Spain. Really easy as its motorway all the way.
Drove back in September, and again it took about 10 hours.
I do know of someone who did Calais - Jerez in about 14 hours but didn't fancy that drive myself.