Recommended transportation back to Irun

We are planning on finishing our summer (July) trek along part of The Norte in Gijon. We are currently looking up transportation options to get back to Irun from Gijon (e.g. train, bus, car rental...).

Has anyone made that journey?

If so, which mode of transportation would you recommend?

How long did this journey take you?

What did this cost you?

Thanks!