Ansett Global Rewards is free to sign up with and covers Air New Zealand, Thai, Singapore Airlines, United, British Midlands, Varig and Lufthansa plus more, supplying you with a fancy swipe card to make you look important. If you're flying your way to the UK there's the Asia route or the US route. The cost is around about the same depending on the time of year but the baggage limit via the states is more generous. Of course there are more flights through Asia due to Australia's position and the service requirements of these countries. It's also a good excuse for a stopover in Bangkok or Singapore.
Travel agents are under pressure to give stopovers due to the large volume of commuters.
They'll put you up in a hotel and collect you for the continuing flight. This is a great little bonus for the budget traveler. Ask the agent about stopovers. You may not have even considered this question. The knee-jerk reaction is to get a return, because hey you've got to come home eventually.