My usually brilliant Pizzey & Knight bird book wasn't immediately helpful, so I asked Google, as you do, with a reverse image search.
Google came up with scaly-breasted munia, or Indian silvertail. Neither are Australian. Then it tried yellow-rumped mannikin. Closer, but only in the Northern Territory. Back to the book then, and after studying the mannikin page carefully, I think I've cracked it. I think they are chestnut-breasted mannikins. There are males, females, and juveniles in there.
