You could try using your 2-4-1 to another Asian city and then buying a QF flight from there. CX flights ex-HKG can be quite pricey unless there is a sale on and you might get better Australian city flexibility with QF.

Alternatively, as this route is quite 'cheap' for what you get, maybe use the 2-4-1 for something else and take advantage of the current (great value) J&F sale ex-UK