Ive got work experience lined up with Qantas here in Perth during November.
I just wrote to them and they slipped me in. But you are right, they fill up very quickly.
Your best bet is to let your school organise it. They seem to know all the connections. Go see your YEO at your school, he should organise it. However, it may be a little late for this year, so If you look into it now, you might be able to get a position for next year.