For what it's worth - I did my PPL and CPL in the UK. Did my ME/IR in 3 weeks in Madrid at Aerofan. No problems with rating issues on my truly blue CAA license. Since done FI there too.
What I would say is this... some snobbery around at the moment about Spanish issued ratings (especially in Scotland?!). Probably fair up to a point as the examiners in Spain are more prone to listening to how the instructors perceive you before you go to test. Less ex-RAF egotism.
In my MCC and more recent airways flying I've had no problem with my instrument flying (as you would hope), and think I can hold my own with the best of the UK-taught crowd. Same goes with instructing. Quietly confident that I can teach pretty well.
Not sure the airlines fancy those spanish issued ratings, but if you can find an interview and prove you're up to it then who cares! I'm going back for a renewal early next month. It probably IS easier to get the ratings there than here, and IS cheaper. My conclusion is that it's up the individual - you can probably pass quicker and with less "talent" in Spain. Up to you how good a pilot you want to be... Happy to answer individual questions via private message. Not biased, in a nice job, and will tell it how i see it (warts and all!).