Probably best to watch a documentary from rapture tv (is that still going?) or on terrestrial when the season gets going. They're usually quite good and give a flavour of the island.
Other than that, can I suggest you go to the Ibiza TV trippin page which is linked via Ibiza spotlight?
Another movie is "Amnesia" by Italian director Gabriele Salvatores (winner of Oscar with "Mediterraneo" 1992)
Don't expect a movie about the club, it's not!
Not his best movie (I suggest you to see his last movie nominated as best foreigner movie at the Academy A. " I'm not scared" set in Umbria, they pretend it's Sicily , amazing movie!).