Do a search on this as i remember seeing alot of threads on here regarding this.
FTE in Jerez i think is probably the one with the best reputation, but it has also been around the longest.I think that this is the only CAA approved FTO in spain.There are others which are not as expensive but i don't know if this has the effect of a drop in standards??
Aero madrid has a pretty good reputation, so does aerodynamics in Malaga.
Bon Voyage