Advice On Secure Sites Bilbao, Spain, going South

AutoMac

We would appreciate advice to help find a secure overnight caravan site about 2 hours south of Bilbao that we can safely use on our planned journey towards Zaragoza in early November 2014.

 We are completely new to caravaning and I'm trying not to bite off too much in one go on the first day of our first van trip into Spain even though we may be able to travel further on the day.



Factoring in the 50 mph towing limit, earlier dusks and a likely time to be off the ferry of 2pm it seems sensible to plan an early 1st overnight. 



If anyone has ideas of secure sites further south in case we make good time then I would be grateful to learn of them too. Thanks in advance!