One answer "QANTAS" . Go and see your travel agent for the other info, deals and advance bookings etc.
They ll have plenty leg room in First Class but youll have to fork out a Kings Ransom to get a 1st Class Seat.
regards
Sheep
P.S. Usually direct LHR to SYD or via Singapore to MEL ,BNE or even SYD aswell.
LOOK AT:
www.qantas.com.au
or try BA as they code share I believe and also use QF routes etc.
But you would get more hits if you put this in the Dunnunda forum.