The ALSA bus company runs a bus from Santiago to Ferrol (at 0915, 1100, 1330, 1430, 1600, 1800, 1930 & 2100 on weekdays; 0915, 1100, 1330, 1600, 1800 & 2100 on Saturdays; & 0915, 1330, 1800, 1830, 1930, 2100 & 2200 on Sundays). From Ferrol, you can get a train on the FEVE narrow-gauge railway right along the north coast to Bilbao and beyond (several services per day). I think you may have to change at various points along the way, but I'm not sure as I haven't yet done this journey myself (am planning to next month!) - see the FEVE website
www.feve.es ; ALSA also have a website (
www.alsa.es ) but I found it difficult to use as it seems to get tangled up in knots when you move your mouse around the screen (you'll see what I mean!) so I got the above timetable by e-mailing them. Hope this is helpful...