I actually like southern Portugal even more (Algarve).

In Spain I would defenitely visit Barcelona.

It has a beautiful old town and an active night life.

I once went to the Dali Museum in Figuera (near Barcelona). I highly recommend it.

Otherwise I'd probably check out Madrid and Seville, depending what area you will be.

Maybe you could let me know what your interests are and what area of Spain you are interested in?

Andre

Travel Photos

Try trip adviser forum. You can find lot of information.

It depends where would like to go. Barcelona, Sevilla, Cordoba,...sea or mountains... 

For me i prefer Morocco. Before i used to go to spain long time ago.

always happy to help
Showmemorocco 

Since you are from the UK, you probably would appreciate some sun.  What about one of the islands in the Mediterranean?  Or southern Italy?

Have you decided already?

 I reccommend you visit Barcelona and the Spanish coast.

-beach, good weather.

-arquitecture(Gaudi and modernism...)

-museums(Picasso, Miro, Dali etc...)

-tapas and good wines. 

-clubs (nice music...)

If you love beaches party, you should try holiday ibiza beach one of the best beach party places in spain.

Well, if you are looking for a hotel to stay in, here are some options. First one is better if you're on a budget, second one is good if you plan to spend quite a bit.

Option 1

Option 2

The others already gave their suggestion on where to go, but I would also suggest Madrid. There are museums there like the Prado museum which is worth the visit.