Aerlingus operate out of Santiago to Dublin as do Vueling I believe. Ryanair fly Santiago to Stansted London then Easyjet on to Belfast. If you get to Dublin go up to St James church at St James Gate and get them to stamp your credencial. Go around the corner to the Guiness storehouse, tell one of the young people at the door that you want the camino stamp and they will bring you to the head of the queue. However you may want to take the tour in which case join the queue, buy your tickets and ask for your stamp. I know it would be better to have these sellos at the start of your credencial but if in Dublin, dont miss out on them. Dont know where you are from but you can fly from Dublin to just about anywhere. If to the States, you can do all your immigration and customs checks in Dublin airport then step off in the US as if getting off an internal flight