Pensioners Living in Spain
All EU and EEA pensioners living in Spain are essentially entitled to the same provision of healthcare as Spanish pensioners, provided they are in possession of an S1 form. British pensioners can apply for the S1 from the Department of Work and Pensions.
You must ensure you have this form with you before you travel and, when you arrive, make sure you register the form at your local social security office. You will then be issued with a social security card, which acts as your “pass” for treatment each time you visit your local clinic or hospital.
If the interim period between applying for your social security card and actually receiving it proves to be lengthy, and you require medical assistance during this time, you can simply take along documentation that proves you have applied for your card and you shouldn't have too many problems.