I live in YHZ.
The YHZ-LHR used to be good for me when BMI was in Star Alliance. I could fly YHZ-LHR-XXX. However now I have to fly YHZ-YYZ-FRA/MUC/ZRH, etc.
As someone mentioned, YHZ-LHR usually always has J award space.
Also, it's a quick hop accross the pond so not much chance to sleep. If memory serves me correctly the flight leaves at around midnight?