No problem if you don't mind cracking on:
!) aim for the camping at
Ochagavia - it's high up in the Navarre Pyrenees but without too much twisties to get there. Once you've had a good night's rest you are right in the middle of some of the best rides of the Pyrenees - I use it as a base for several day's riding . . .
They also have cheap hostel type accommodation if you arrive in the pouring rain - and the food is great too!
2) if you're late, delayed/dismayed by weather, etc, you can cut your trip shorter by stopping at
Lumbier. Quite a nice camp site but just outside the Pyrenees so the weather is more reliable and it's just off the end of the Autovia - but well away from it.
3) otherwise, just run up the coast a bit to
Mundaka: like most campings along that coast it is expensive, but it has 3* facilities.
I read your stuff about the need for registration -
my partner is traveling on a Schengen visa and part of the visa requirement is we have accommodation booked.
In Spain all campings have to record people's details, passports, etc. so no problem there. But of you have to book then go for Ochagavia and if there is a problem just don't turn up. Ochagavia is a municipal camping so will take bookings, especially for the hostel.
I imagine that once you are in Spain you are footloose and fancy free - Spain being in the Schengen zone . . .
Regs
Simon
