Hi Jim,
I assume if you are retiring here, you will also become residents. So as long as you are over 65 (retirement age here for men and women), you will be entitled to free Social Secutiry (i.e National Health). This also will include free prescritions. But of course you will have to register here etc.
Make sure you speak to Newcastle before leaving and get all the correct forms. (As long as you will be staying here more time than in the UK.. some people like to go back and forth and keep their UK doc… But I am sure you will know that anyone staying in Spain more than 3 months per year is supposed to register as a resident.) Read up as much as you can on this before making this commitment… also ask as many Q’s as you need to!
Good luck with the move.
SJ
PS - If for any reason you need to buy your medication, many prescription drugs here are available at reasonable prices. (Although my migraine meds are Eu44 for just 6 tabs, where I get a prescription for 24 for 7 quid in the UK :(