One of the problems about Spanish ATC is the lack of consistency. While undoubtedly some controllers strive to do a good job most of their colleagues lack of proficiency borders on the downright dangerous.
I suspect they simply deny their shortcomings just because they don't know any better. It would do the Spanish controllers a great favour to take a tour outside their borders, and see how German, British, Dutch, etc ATCOS do a far more professional (and safer) job.
Sonnendec:
This thread is not to hurt your feelings, but that's just how the majority of pilots in Europe feel about the quality of Spanish ATC. They fly to many destinations, all the time. Why do you think they've picked on Spain and not any other country?
If you wish I can arrange for you a jumpseat in the cockpit to anywhere you like within Europe, so that you can compare Spanish ATC with all the others. I'll leave it up to you then to decide if we are right. Do you accept the challenge?