Just guessing at travel to some of the less known places. Correct me if I am wrong:
Viktoria Plzeň CC >> Prague
Freiburg CC >> Hamburg or Bremen
Celta Vigo >> Porto? Nearest Spanish airport?
Go Ahead Eagles >> Amsterdam
Brann >> Bergen or ??
Airport in Vigo served by Ryanair but not every day. Santiago de Compostela has daily Ryanair flights - about an hour's drive to Vigo.
A few other possibles:
Braga are a cert - >>Porto
Genk are a cert - >> Eindhoven, Brussels
Midtjylland a cert - >> Aarhus
Ludogorets probable - >> Varna
Utrecht probable - >> Amsterdam
Malmo very likely - >> Copenhagen
FCSB likely - >> Bucharest
If Samsunspor get through - that is more of a challenge via Istanbul
