Adding yet more info on the youth-hostels (called "Albergue Juveniles" in Spanish) visited:

Sevilla Albergue Juvenil: nice and clean place to stay, very easy going staff who prepared our packed breakfast for early departure in the morning. See http://www.inturjoven.com/uk/redalbergues/sevilla/ajsevilla.asp for more info.

Quo Qadis in Cadiz:lovely building in the old quarter with loads of tile mosaics on walls and floor. However, prooved to be a problem communication when for the cost of 6 euros we were shown a room so called Japan just on the roof - a very tiny and unclean room (if I could call it a room - no doors, only separating "paper wall" between two dorms of four, where the two bunk beds were placed on some 9 square meters - a bit of safety concern for our belongings if you ask me, not mentioning the fact that if you are brave enought o sleep there you must not be taller than 1.5 meter to fit your legs in). Later we got two beds in a room for four (great company of a Pamplona lady and a REEEEEAAAAAALLLLY badly snoring man - now we would have been so happy for the earplugs MM!!! ), cost 10 euros per B&B per person. Sadly, I would not choose this place again - certainly would be looking for slightly more costly hostales elsewhere in the city but having this CLEAN feeling)

Palice