I live near Stansted Airport and Air Asia have recently started flying from Stansted to Kuala Lumpur in Malaysia. I noticed one of their planes today so looked them up on the web. Air Asia are based in Malaysia and from there they fly to Melbourne, Perth and the Gold Coast (plus many destinations in Asia). They are a low cost budget airline, so you have to pay extra for meals etc, plus it seems that you don't have a baggage allowance but pay for how much you carry.
I have absolutely no idea how good they are, but Stansted Airport is a lot nicer than Heathrow. I priced up a one-way ticket to Melbourne in August 2009 (without the extras) for 4 people and it was £1403, whereas on Singapore Airlines it was £2302 (2 adults 2 kids). They fly airbus A340s out of Stansted.
Just a thought, another airline to investigate, could be a lot cheaper than the conventional airlines. see www.airasia.com