What is the correct etiquette please?
You need not quote directly from Debretts.
If I weren't in the queue for the soggy salmonella sarnies left in Tescos- I'd write a longer OP. 
Part Two here: www.mumsnet.com/Talk/_chat/a2631196-My-colleague-has-twat-me-over-the-head-with-a-courgette - edited by MNHQ