So I managed to find availability to fly LHR - BNE (via MEL) with Qantas without any stopovers.
Unfortunately I can't find any suitable with just BA or Qantas unless I stopover, which I'm not really inclined to do. However I've found that I can fly BNE - SIN with QF and then SIN-HEL-LHR with AY.
Due to the 2 partner rule, it costs a lot less miles to book this as two seperate awards, costing 50k and 80k, I believe it would be 160k in one booking. Is there any downside/risk to having 2 bookings. The connection time in SIN is over 3 hours so there shouldn't be much risk of a misconnect.