You should also look at ex-Australia fares.
I would be interested to learn more about the 3/4 continent fare - they list a max of 4 segments per continent and 6 segs in Nth America with backtracking allowed.
Does that mean you can do SYD - LA - NYC- SFO-NYC-SFO-NYC-SFO-LHR? (Is the SFO-LHR segment counted as Nth America?