A good pub session needs an area reserved for the music making. A landlord who will not provide this does not deserve the session and the cash it generates for him.
Session members who forget themselves just need reminding. I can only sing unaccompanied and without mics can cause me problems with a quiet song. I try to make eye contact and make a pleading (not angry) expression. It usually works for me. It helps that I stand, and sing eyes open.
Keith.