Hi there,
Well, you could try to fly into:
1) London...then take Ryanair to Santiago (then bus to Sarria via Lugo)
2) London, then EasyJet from London (Stanstedt) to Oviedo (airport called Asturias), then train (
http://www.renfe.es) to Lugo and bus/taxi to Sarria.
3) Barcelona, then take Vueling (Vueling.com) to Santiago, and bus from there to Sarria.
4) Madrid and take bus/train to Lugo and bus/taxi to Sarria... or get a cheap flight from Madrid to Santiago (see
http://www.spanair.com http://www.iberia.com http://www.aireuropa.com )
5) Porto is an option, I think you would have to go via Santiago to get to Sarria.
For some links to bus companies in Galicia, have a look here:
http://www.santiago-today.com/bus-sched ... ostela.cfm
(some of these schedules might be out of date)
I hope this at least gave you some ideas...
Welcome!
Ivar