Santander sites open in January

Do you need one?  The ferry from Portsmouth arrives at 0800 so you can go on your way that day, and the return sailing is at 1400 so you can  drive to the port in the morning from some distance away.

But if you really want to stay then Camping Virgen del Mar is usually open all year although I have an idea they don’t accept dogs. 

tks they are "No Pero"

"Do you need one? The ferry from Portsmouth arrives at 0800 so you can go on your way that day, and the return sailing is at 1400 so you can drive to the port in the morning from some distance away."

it just makes it easier to sort out a vet and get the dog sorted, has to be wormed not less thqn 2 days before departure and no more than 5, going out Portsmouth Caen so no probs with that, returning Santander - Portsmouth, could stop over at Zaragoza for a couple of days and still make the 1400 sailing, even Larrouleta is not a bad option, 3 hrs to the port perfectly doable.

We have used Camping Fuentes Blancas in Burgos. Its about 120 easy miles to Santander.