I think a price comparison between a through ticket PER-SIN-LHR-USA and 2 separate tickets PER-SIN and SIN-LHR-USA might also in order.
The latter (I think) is certainly cheaper if you can get to SIN one way and base future tickets from SIN. ie the SIN-PER-SIN is much cheaper than PER-SIN-PER
The only other option I am aware of is the BA/QF WT+ Australia-Europe excursion fare which permits the return back through Asia or through N or S America based on a European turn point. The BA segments book in W class if premium is available, the QF segments book into B class.
Actually more beneficial for AA FF members qualifying via qPoints than QF FFs
If there are other options I would like to know about them....
Happy wandering
Fred