The potential hornet's nest here is the transfer of medical from one Member State to another, should an individual wish to switch training between EASA countries.
As I understand it, if the OP's initial medical is issued in Spain and at a later date he then wants to train for a further licence in the UK, the UK CAA will require the medical to first be translated into English by the AME then passed to the Spanish aviation authority for endorsement before being forwarded to the UK CAA.
Clearly this won't be a free service and leaves me wondering how much all of this will cost and how long it will take. With one doctor and two aviation authorities involved I assume it could amount to three separate fees.