The  Int'l Certificate of Competence is not recognised by the Spanish if you are skippering a Spanish reg'd boat.  However, it is sufficient if your boat is British and SSR'd (and of course you have a VFH radio licence).  If you have a boat here and you have residencia then the wise thing to do is transfer ownership to a person (family member?) in UK, not forgetting to tell your insurer s (and having an ins. cert in their name plus a written permission from them for you to sail their boat).  There is absolutely nought against a UK resident having their boat here 12/12 months; the issue is the owner being skipper being resident.  Therefore, don't be.

The ICC is issued by the Royal Yachting Assoc and is based upon a series of theory and practical courses, instructions and exams.  They are all based on supporting a voluntary education/training program - unlike the French and Spanish mandatory approach - the RYA encourages further and on-going traing.  Support it if you can as it's the best scheme in europe and copied (oops, franchised)across the world.  There is a local RYA instructor/ examiner but he seems to keep a low profile.  Let me know if you want details.