Hi Jme,
I live in The Blue Mountains west of Sydney. I walked The
Camino Frances last April. After I got to Santiago, I spent a few days there, did a day trip by bus to Finisterre and back. Almost 3 hours each way but a great trip that day, sunny and warm. Lots of water views along the way. I had lunch, walked to the light house, and got back to Santiago the same day. Santiago main bus station is about 45min walk from the cathedral.
I flew Emirates, big baggage weight limit, and they fly in and out of so many major European cities that you can fly into and out of cities of your choice - mix and match, no extra charge. Santiago airport is pretty big - not at all crowded in early May. I flew from there to Paris, then out of Paris later. I had flown into Madrid in March, stayed there for a few days, train to Pamplona, bus to Saint Jean. You could fly international out of Madrid after a domestic connecting flight from S. which would probably be pretty cheap.
Buen Camino, - Mike