Where to camp in northern Spain?

[unlikelychump]

We are taking the caravan over on the long ferry, started looking for campsites now. Any recommendations. We are thinking of a few nights in llanes and a few in/near San Sebastian, then over to Biarritz and head north.

We've been to France plenty but never Spain.

Hello. Did you end up heading to Northern Spain? How did you find it? Any campsite recommendations please?
Planning a similar trip next year!