In answer to your last paragraph PG, most English festivals use small venues with no separate "backstage" rather than concert halls or theatres.

Most "established" performers that I have come across have been great people. Usually the arseholes never get established because they piss off too many customers on the way.

I can think of one band where one member clearly has the job of smoothing feathers that his colleague at the front of the stage ruffles. He is noticably careful to make sure that whoever controls the power supply is happy, an annoyed caretaker can be very prompt about pulling plugs and throwing light switches.