not sure how much it is to hire a post box in the post office...but our village (Bitem) as I would guess in most villages has an "English" box......where all the mail from England ends up if there is no post box in your address...you just need the code of the village "Correos", and then you just call and ask for the box and sort through for anything with your name on it!!  (or indeed of your neighbour if you feel generous enough to drop it off for them!!).  This service is free. :)

Liz