A friend of mine was able to get 600 euros compensation for a flight cancellation he experienced coming back to Oz from the UK.
Given my own flight cancellation a month ago, I decided to investigate further.
I contacted Qantas about my cancelled flight late last week. Sure enough, I received confirmation that I am entitled to a 600 euro refund too! Evidently flights coming out of EU countries are bound by regulations that specify compensation for cancellations and delays. Because I got back to Melbourne almost 8 hours after my scheduled arrival time, I was entitled to the compensation. Yay!