Great to hear from someone who wants to put something back into the pilgrimage as hospitalero.
As Jeff001 says, the Confraternity of St. James, England, have two refugios, one at Rabanal del Camino, just after Astorga on the Camino Frances and a second on the Camino del Norte.
Your qualifications are perfect for what the CSJ ask for - to have done the pilgrimage and have some Spanish.
I'm not trying to top Jeff but having worked at Rabanal I can tell you that the Hospitalero Co-ordinator for Rabanal is Tricia Shaw and she will be able to help you re Rabanal but will also be able to give you the E-mail address of the Co-ordinator who deals with the refugio 'Miraz' on the Camino del Norte'. If you deal only with the CSJ it ties you to their own refugios but the advantage is that for your first period, at least in Rabanal, you would work with experienced hospitaleros.
However there is also, I believe, some sort of central co-ordination within Spain, whereby you can volunteer and they will allocate you to a refugio. Again, I think the CSJ could help you with this.
So finally Tricia Shaw's e-mail address for CSJ information: email@example.com
I've done the Camino twice (the co-ordinators want people who have done the Way at least once) and recently finished a 2 week stint at the guest house in León as hospedero. It was an excellent experience. It teaches one flexiblity, openness and ceertainly tests your endurance. It's a lot more demanding (depending on the guesthouse) than you might image.
But it's also good to have something more than the Spanish and English. I would up with "cheat sheets" of the basic comments (How old are you? What nationality? etc in Italian, German, French...
and while there were a few pilgirms I was happy to see the back of, most gave me a bit more faith in my fellow humans.
But if there are problems, it will be with the fellow volunteers. The pilgirm is on the way the next morning. You have to live and work with the other volunteeer (s) for 2 weeks. But go for it. And the best reason is to give something back to the Camino. After all, it gave me so much.