In reply to Nigel R Lewis:
There is a Spanish equivalent of 1:25,000 military grade which is probably the best, but having said that don't expect the high quality of our OS maps. At best I would say that they are good as indicative tools, but in my experience are full of errors. One of the reasons for this seems to be lack of recent upgrading, particularly in rural and mountainous districts where farmers are constantly making new access tracks, and allowing others to fall into disuse.
The terrain suffers from regular flash flooding, and occasional earthquakes, resulting in landslips causing tracks to get washed away or blocked, so the farmers bulldoze out diversions. Also tracks serving high terraced fields, forests and olive/walnut groves don't necessarily go anywhere other than to individual fields, and mountain ramblers/gullies, before petering out, and what you find on the ground bears little relation to what is shown on the map!
I had a set of these maps military covering the Filabres Mountains bewtween Baza, Huercel Overa and Mojacar, which I got from Stanfords. It might be worth your contacting them for your area?
As you are in Murcia, did you know there is a rock climbing guide book in both Spanish and English covering the Sierra Espuna? ISBN 84-96396-09-6
Hope tis is helpful