In reply to Oujmik:
Cicerone do a guide - 'Picos De Europa Walks and Climbs' - it retails for £12.95
I've got one (almost new) you could have for £6.50 posted if you get stuck.
Also, just to hijack the thread a little, if anyone needs a copy of the climbing guide 'Cordillera Cantabrica Escaladas Selectas En Roca', I have one for sale also...