Most places you have a munch in are normally ok with whatever happens in their function rooms... as long as they are informed 1st.
the last munch I organized in Leicester the landlord had closed his doors to the public for the evening and afterward actually invited us back!!! said him and his staff hadnt had that much fun on a sat night for ages!!
as you say... most munches are advertised via listings and forums... I get a load from the midlands right thru to bedfordshire etc etc also I know whats what and which club is best and am kept in the know about what demos are being done that month.
cg