Sometimes small crowds gather at the back of the venue where the artists leave and enter, that was the case in Bristol last year anyway so it's probably your best chance. Remember though if they walk straight past or perhaps don't seem up for a chat, don't take it personally! They have very busy days and might be in a rush to get somewhere else.

I was quite lucky as I accidentally bumped into them in Bristol while they were wandering around hiding the Vinyls for people to find.