Sydney is a popular target destination for using frequent flyer miles, probably because the sheer length of the flight means that people are keen to do what they can to avoid travelling in economy.
Ironically, redemption tickets to Australia and New Zealand are often poor value. Mile for mile, buying a cash ticket to Australia in a premium cabin can be relatively cheap. You can often find a business class ticket to Sydney for around £2,000 – although you may end up starting your trip in another European country and flying on an airline you wouldn’t usually consider.
In contrast, an Avios ticket in business class to Sydney is 200,000 points plus taxes. Even assuming that you can find availability – very difficult since the service was switched from 2 x daily 747s to 1 x daily 777 – it is not the best value.
As per the last couple of pages of this Flyertalk thread there are some good British Airways prices currently available out of Oslo. This obviously involves you flying to Norway – at added cost – and then flying back.
The current price at ba.com (book by 8 September for departures in January-March 2015) is 21,547 NOK or £2,059.
The fare rules actually allow up to five stops on your routing. The Flyertalk thread shows, for example, how you can do Oslo – Heathrow – Singapore – Sydney – Perth – Brisbane and back for £2,102. Throwing in Auckland as well gets you to £2,173.
You would also earn a huge amount of Avios points from the flights and probably British Airways Silver status as well, depending on routing.
You can find more details in the Flyertalk thread above – apologies in advance if you find some of the acronyms confusing!