BA009 only runs LHR-BKK (and vv). The BKK - SYD leg was dropped in March.
If you are travelling onto to SYD you will have a multi-hour layover at BKK. There are joint lounges between BA and QF for F and J.
I have pictures of the J lounge which I will try and upload today - I have an overdue trip report relating to my first journey in J (which was BA10 - BKK - LHR).