Questions

I think a visit to these websites might help you with your plans.

http://www.caminosantiago.org/cpperegri ... norte.html

The route follows the coast and is called the Camino de la Costa from Irún, Oiartzun, Errenteria, Pasajes, San Sebastián, Orio, Zarautz, Guetaria, Zumaia, Itziar, Deba, Mutriku, Markina, Zenarruza, Mendata, Guernika, Larrabetzu to Bilbao.
Click on "Albergues" for a list of refuges on the route.

And Eric Walker's site:
http://www.gawthorpe40.freeserve.co.uk - lots of info on the northern routes.

http://www.csj.org.uk/route-coastal-route.htm - gives a list of guide books