The option you mentioned of QF9 MEL-SIN connecting to CX2074 SIN-HKG is a good one (even if a bit boring as you say).
On the way back to London obviously something along the lines of CX709 HKG-BKK connecting to QF1 BKK-LHR would be a good extra segment to put (though might be too short a transit - you can always catch CX703 to connect to the earlier BA flight as well).
That way you're looking at just an hour or two in the airport while you switch planes, and not *too* much backtracking from Singapore to HK, and heading in the right direction from HK to BKK. Both flights have first class and are a bit over 1,000 miles so you get better SC's with Qantas than a shorter leg going to Taipei or SIN-BKK.
[This message has been edited by GibSpmuh (edited 08-12-2003).]