On HKG-LHR and HKG-SYD, two of the most high yielding premium routes in the system, not likely. Sometimes even full fare availbility can be a problem, especially on LHR.

In short, I would not expect an upgrade for anything short of the difference between your fare and the appliable F fare.

That is, if they even have seats available. If you are originating from LHR, I would see if you could get a good A fare, or else, 99 times out of a hundred, you will not be in F for anything short of a F ticket. This is not AA or UA.