Thank you Tio Tel!
To avoid starting the walk from not-so-pretty Barreda heading to Santillana (asphalt surface all the way), the Spaniards suggest taking the very same FEVE train, but getting off at the
next stop after Barreda, the town is called TORRELAVEGA. Supposedly there are frequent buses from there to Santillana, and they stop at the front of the train (FEVE) station. That's what I heard from the locals.
In Santillana there are (I think) two albergues, one is the municipal one, there are just a few beds so they prefer to offer the place to those who walked from Santander. In the summer, when they run out of beds quickly, they seem to be strict about it. There is a second albergue, private, on that cobblestone street, quite nice, the hall has a very 'antique' feel and they have dorms as well as private rooms. They accept everyone, not only pilgrims. Both albergues are listed in Eroski guide:
Albergue municipal Jesús Otero
Albergue Solar de Hidalgos
There is also a camping where the pilgrims are placed in very old, small, cramped, and claustrophobic camping huts. I just looked inside and left. I wouldn't recommend it to anyone. But I can recommend the camping huts at the camping Deva just before Gijon. Those were nice!