On summer, you can fly twice a week from Vancouver to Biarritz changing planes in London (Heathrow) with British Airways. Once in Biarritz, you can take a train to Hendaye and walk or take a taxi from Hendaye to Irún (on the other side of the river) or take a local Euskotren from Hendaye to Irún (the Euskotren departs from a train
station on the parking of the SNCF train station).
Airlines flying from Vancouver to Bilbao with just a single change of planes include: Air France (changing planes in Paris CDG), KLM (changing planes in Amsterdam) and British Airways (changing planes in London Heathrow). Once in Bilbao, you can take a bus to Irún with Alsa (
www.alsa.es/en).
I don't know what are your plans after your camino but how to get back to your home town is something relevant (unless you don't plan to go back home). If you plan to return to Vancouver right after finishing your camino, to make it with a ticket issued by British Airways would mean two changes of planes along the route and to make it with a ticket issued by Air France or by KLM would mean not only two changes of planes along the route but departing from A Coruña airport because they don't offer options out of Santiago de Compostela.
Iberia codeshares the route from Vancouver to Bilbao (changing planes in LHR) with British Airways and codeshares the route from A Coruña to LHR with Vueling. Therefore you could get an open-jaw ticket with Iberia outbound: Vancouver-Bilbao; inbound A Coruña-Vancouver even though Iberia doesn't operate any of the fligths you would take. Take a look at the web of Iberia for info about fares. That's a convinient option because involves just a single change of planes both outbound and inbound and it's all ticketed together so if you miss some flight due to a delay or cancelation of the previous flight the airline(s) must search an alternative to get you home. To get from Bilbao to Irún is an easy bus ride (see above the web of the bus company). To get from Santiago de Compostela to Coruña is an easy bus or train ride; pick your choice. There are buses too from Bilbao airport to downtown Bilbao as well as from downtown A Coruña to A Coruña airport.
If you choose to make separate bookings (e.g.: a booking from Santiago de Compostela to London and another one from London to Vancouver), don't forget to allow yourself enough time to get your connection because if you miss it by any reason, you would have to look on the spot for alternatives to get from London to Vancouver and, most likely, it won't be cheap at all.
P.S.: A Coruña airport IATA code: LCG
Bilbao airport IATA code: BIO
Biarritz airport IATA code: BIQ