McPat,
You say you arrive at 8pm at Santiago Airport.
A bus stops outside airport at 8.10pm and you arrive at Sarria at 11pm, 3 hours.
If you can dash from plane, and run outside Airport, second stop on right,
and wait for bus Empresa Freire travelling to Lugo.
It is a small airport.
This is the last bus for the day.
The trip to Sarria comprises 2 buses, Santiago to Lugo, 2 hours arrives Lugo 21:55 price approximately Eu 6, bus company EmpresaFreira, and Lugo to Sarria departs from Lugo at 22:30 and arrives at Sarria at 23:00 price Eu 3.40, bus company Alsa, same bus station at Lugo.
Lugo is a beautiful walled town.
By the way tickets can be purchased on bus.
I took this bus on the one and only time I have walked the Camino.
Hotels in Sarria, I stayed in Hotel Oca Ville de Sarria, and found it comfortable and very close to start of Camino.
Remember, if booking , to deal directly with Hotels, as has been demonstrated on this forum and elsewhere, If you cancel with an internet booking site, you can lose your money.
Web pages of bus companies, times and prices are given
http://www.empresafreire.com/
and
http://www.alsa.es/
Web pages are in Spanish, can be translated.
A wonderful browser which I use instead of Internet Explorer is Google Chrome, which translates the pages immediately, wonderful on Spanish web sites, download now at
http://www.google.com/chrome
Times of buses from Santiago Airport daily to Lugo are
7:10 11:10 16:10 18:40 20:10.
This same bus leaves Santiago de Compostela 10 minutes earlier.
Times of buses from Lugo to Sarria daily from 12:00 on are
13:45 18:35 20:45 22:30, duration 30 minutes.
I have obtained these times on above bus companies for date Sunday 4th September.
BUT McPat,
You said flight arrives at 8pm, but I have checked Ryanair from London Stansted to Santiago de Compostela on Sunday 4th September, and it says it arrives at 20:50, i.e. 8:50pm, so you have missed last bus, and will have to stay overnight in or near Santiago, can you check ?
If so , you will not need stay in Sarria, but get the morning bus to Sarria, and start walking from there.