Tuesday's Beech Band in Manchester has its own chorus book to get everyone singing the same version.
http://www.folkatthebeech.org/singing-songs.html

Doubtless Les can tell us how well it works.
(btw Les, I did a version of it for printing on a printer that does the two sided duplex thing)
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I think
join in on the chorus if invited.
don't join in with the verses! Even if the performer can't hear, the person sitting next to you can.