If I only had 12 days, then I'd spend it in Andalucia.
I'd fly from the UK to Malaga......The places I would not miss, would be.
Malaga, Sevilla, Granada (Alhambra palace), Cordoba, Jerez ( home of sherry and Alcazar/Arab baths)
Then, you have Ronda, Marbella, Gibraltar (uk) and Cadiz, plus Huelva (around the Costa la Luz) to the border of Portugal.

IF I had 112 days, and was driving through Spain from the UK, then the list would be enormous.

Sanji x

Hy!
If i had 12 days, i would definitly visit Castilla y Leon (Valladolid, Á vila, Burgos...).
The traditional touristic cities are so crowded and so visited... that it makes you want something else.
I visited Castilla y Leon and i felt like i belong there.
jcyl.es Here's a site for you to get to know Castilla and to help you drive around. I have a dear friend who lives there and she uses this one alot.
I hope you'll get to visit Castilla y Leon.... in my opinion is the best region in Spain and has some of the most fascinating people i've ever seen.

Seville would have to be on my list, I think it has to be one of the best cities in Spain and I just love it anytime of the year!

I would suggest visiting Barcelona, Valencia, Merida, Ronda and then Granada, covering Spain from north to south and experiencing the different cultures and lanscapes that this wonderful country possesses.