www.thebasource.com is reporting BA's latest B777-300ER G-STBH has positioned from Cardiff to Heathrow and will enter service as BA15 LHR-SIN-SYD departing 5 Nov. London time... this would put it in SYD tomorrow (Thursday) morning assuming no changes
Edit: Flightaware has finally caught up, G-STBH showing as having entered revenue service on BA15...
http://flightaware.com/live/flight/GSTBH