For me in F I would take the BA28 HKG-LHR:
You have an OK lounge with BA/QF
The CX lounge is a 10 minute walk and is great (it is the CX flagship)
Nice long flight and good times for sleeping
Guaranteed NF
777-300 which in F is a much better cabin in my view compared to the 747-400
Also if it is a long lay over then you can get into HKG itself with the train in 20 minutes.
FD.