Well I have had to deal with that kind of thing in the past, I find the best way is to be direct about it and firm (helps if you look like a bit of a bruiser which I do apparently). Just go round and tell them what the score is, if they give you any crap then call in the authorities. I don't mind a party now and then, hell I was playing rock band and playing on my decks with a bunch of mates until 4am last night but if it was every weekend I would probably have something to say. Week night partying is unacceptable as far as I am concerned though.