Yes that's the one Peter, I think it is a reasonably well-known film - it is hard to gauge these things from the perspective of other countries. It was made in 1975, directed by Peter Weir who also did The Truman Show, Dead Poet's Society, The Year of Living Dangerously, Gallipoli and also The Cars That Ate Paris - you really know your films if you've heard of this one, I actually saw it on tv once.
The film is based on a book by Joan Lindsay, and set in 1900. The plot is simple, a group of school girls go on a picnic at Hanging Rock (yes, really) and disappear. Although it is a novel, there was always the rumour that it really happened, which added to to the aura & mystery of the film.
The actual place is quite interesting too.
http://www.hangingrock.info It is "a rare volcanic formation of solvsbergite situated in the Hesket plains". It is like a hill of rock, with crevices everywhere, and because it is surrounded by trees and it is always very quiet there is a sense of isolation.
Photos to come from the car show (eventually)