Forget all the above, the OP is travelling on QF29 HKG-LHR
on 25th Aug in which case the aircraft is a 3 class Kangaroo route 744.
This aircraft is schedule to depart MEL on 24th August; hence the confusion (from my, and probably the agent).
35C is indeed in Economy.
Seat Map:
Expert Flyer is return the same seat map for W class and Y class.
Loadings HKG-LHR are thus:
F3 A3 J0 C0 D0 I0 W0 T0 B9 H9 K9 M9 L0 V0 S0 N0 Q0 O0 X0 E0