Thanks for the advice Tom. I had thought about taking the Euskotren
although i'd need to take the line into Bilbao and then change trains
twice. Plus the train takes 2 hours to get the 50 km or so between
Bilbao and San Sebastian. I will see if i can find some info on that
bus company though as that would be extremely helpful.

As for the previous post of flying into San Sebastian directly. I'd
love to do that however there aren't any budget flights there from the
UK and the cost of flying elsewhere to fly into there just seems to
waste more time than it's worth. If anyone has any other info it would
be much appreciated. Thanks to all for all info on this matter,
Matt