Hi Thornley,
Sorry I do not remember Liando as did Castro Urdiales to Santona in one day, but would not recommend this unless good weather and you are fit.
We (I & my polish walking companion at the time) were intending to stay in Laredo but the municipal albergue was only to open (I think 17:00 hrs). I recall a nunnery doing overnight stay, too, but we passed it early as one comes in to Loredo and no movement in there in the afternoon. So I strolled the beach (paddling barefoot to ease sore feet & blisters) to Santona. It was May without tourists so was excellent. It is about 6kms, easy walking with a small ferry over the estuary to Santona. Municipal albergue is the sports hall, clean, friendly, small but crowded rooms. & they do breakfast. Santona was very pleasant, smaller and more 'convivial'. We did not find any 'pilgrim menus' in town but believe the albergue had a canteen type set up. Nice town.
The walk to Guemes (which, yes, is a 'must on this route' can be readily done 22kms or so) starting off on great coastal walk once out of Santona. Guemes alberge was for us a bit hard to find but then the centre of Guemes was too ! It is on the west side and 2 kms off the coast road & with no obvious sign from the road. Apparently there are signs which go over a track into the fields but we missed it. Lots of beds and space. Don Ernesto & his team pride themselves on cleanliness and friendship (& good simple food which all pilgrims eat together).
Guemes to Santander is excellent coastal walking. Wonderful views on cliff tops and then beach to get another ferry into Santander (from Somo). A shortish walk to Santander for 1 day but too far to gofurther to municipal albergues that I knew of.
Out of Santander is straight and on road for some time. Crossong the 'illegal train bridge' at Boo de P. is fine, locals fishing off it. If you are sensible it bears no more risk than crossing a road, but its uo to you. Santillana, small, medieval and touristy but most depart by 20:00hrs in May. Nice cathedral, good albergue but smallish, limited space.
Comillas was small old town and lovely location, although we didn't stay long and walked on to Serdio/Estrada. Municipal albergue was good & clean, we settled in before anyone arrived and were given the key to lock up after we left. Has a kitchen but don't recall a shop. The small local bar 200metres away, was friendly and very country spanish (with bullfighting on the omnipresent telly). We had a major fish based 3 course meal and wine all for €10.
Onto Llanes was then difficult with a major road being built and going onto a Spanish walking route which was fine but added confusion and distance to the route. Would not surprise if me they are still building 1 year on.
Hope some of this helps.
Enjoy, have fun - Valdis.