Cell phones and Sim Cards

I guess that a lot of people take their cell phone not only to use for communication but as a camera. The quality of photos is certainly great, saving weight and space. I use my cell not to phone out particularly but so that my wife can phone me from Vancouver after my day and at the beginning of hers. My query however is regarding getting a Spanish SIM card. This spring I was on the Norte arriving by ferry from England and I was able to get a SIM card and very reasonable monthly plan in Santander at a Vodaphone store. However, if one starts the Frances at SJPP one is in France and if one arrives via Bayonne presumably one has to wait until one gets into Spain to get a card; however, I sense that there are no outlets of the major providers in the smaller towns where one can get a plan as opposed to an off the shelf card. If one arrives at SJPP via Madrid or Barcelona I suppose one can get a card and maybe a plan at the airport, but I think at more expense unless there is an actual phone shop. It would be good to hear of the experiences of other pilgrims. Thanks.