You have not missed the boat as the boat did not arrive.

I have stayed up until midnight for weeks (without success) chasing Xmas/New Year BA first class seats from LHR-SIN-LHR.

The big question is will the boat arrive (I do not think so) BA can sell every seat on the SIN-SYD-SIN route over Xmas/New Year, they are even very tactical with the release of A class seats on this route so are they going to give any Z seats away?

If you want to use the 2-4-1 to SYD you will have to be very very flexible and maybe plan your trip nearer to the Northern Hemisphere Summer. Everything changed on this route when the BA/QF JSA ended.

I would not wait around for BA award seats I would grab the CX ones as suggested up thread.