I flew nonrev on QF LAX-SYD-LAX without any problems.
I used to work for WN and I remember them not having many ZED agreements. ZED is the best way to go since the tickets are inter-changeable on any ZED carrier. I was trying AF SFO-CDG and it was full and so I just used my same ticket on VS SFO-LHR.
I did not care for the way you had to buy tickets in advance from the pass bureau at WN.
At my carrier, we can purchase nonrev tickets from any of our counters worldwide, even the same day of travel.
Best of luck to you getting to Perth!
Let us know how it went.