Didn't Victor Meldrew have something to say on this very subject??
For me the problem with your premise for a sitcom Bushbaby isn't so much the first story as you describe it. WHether it would be believable or not would be in the execution, I haven't read your script so I wouldn't have a clue.But for me the party planning premise is kind of unbelievable for a series, every week they organise a party with disastrous and hilarious consequences. You seem to be describing that as the engine of your show and I don't think you need to. The situation is them all sharing a squat or a house or whatever. Root the premise in some kind of perceived reality and each episode would be about the characters and not the 'sit' per se.