ArtMan things aren't too different here to the US, at shows with 'big stars' you'll often find barriers set up and security who will organise the stage door situation, others may not have this it depends who/what you're going to see.
30 minute rule applies here too, personally I don't like to stage door pre-show, some may say it isn't the best time to bother a performer and that it is better manners to stage door after the show as you are then able to compliment the performance etc, this is a matter of personal opinion.
Generally if you're polite, don't push anyone out of the way or make rude comments about anyone you'll probably be better behaved than some of the brits present!
Maybe I'm on nobody's side
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