I'm not sure if HK immigration has got any better of late, but I think you will struggle to do anything meaningful with this itinerary. Can't see you being in the Novotel before 11pm (note they have a free transfer bus for guests too) and I believe this is about the time Temple Street night market closes anyway.
Can't you leave SYD a day earlier or get to LON a day later? Seems a waste to spend such a short time in such a great city.