This might be a massive longshot, but I have flights from Perth to London in July. There is a ‘bid’ option to upgrade, but I don’t like my chances.
Is there any backdoor routes that I could use to upgrade or potentially get a business class seat? For example, upgrading using Asia Miles or through some sort of partner arrangement.
Only two paths to upgrades with Qantas I’m afraid:
Using Qantas Points
Bid with cash (or a mixture of points and cash)
Qantas Points or Classic Flight Upgrades will be processed first according to your status (and if the same, the time of submission) at the designated time before cash bids are considered.
While increasing your bid amounts will increase your chances, being a high status Qantas member would help more. Additionally, you can increase your chances of scoring an upgrade by selecting the upgrade at the gate option which means you might get a Premium Economy seat instead of a Business upgrade or a Business upgrade if one is available.
Given the popularity of the flight, it is unlikely that you will have much success with the upgrades so just set your expectations.
Unrelated to your specific enquiry, but it might help others. I was successful in upgrading to Business on my flight from LA-SYD by picking an A380. More seats = more chance of upgrade. Upgraded using Qantas points.