No specific details as yet, but the Flight centre often have Flash Deals (haven't seen any for a while). Just had email that from 10am Tuesday (tomorrow) they will have flights to Melbourne for £449. Keep an eye on their Twitter and Facebook pages as they may announce further details such as airlines and dates.
Screen shots to follow, but you'll need to call. In my experience you need to get on the phones a few minutes before.
Screen shots to follow