Sounds really appealing. Going from a warm tropical climate with affordable food, good transport, relatively good social services to somewhere cold, wet, lower standard of living, and in economic turmoil.
It’s subjective but I personally find UK’s cold wet weather much more tolerable than HK’s moist and hot summers and winters actually feel colder in HK.
HK’s public medical system is no better than the NHS.
As for standard of living , you are joking, right?
It would probably be fairer to compare Hongkong with London because the UK is obviously a large country (compared to HK, essentially a single city).
The UK has some nice places but also many ghastly ones (it has both the wealthiest and most deprived areas in Western Europe). London is different from the rest of the country in about all aspects.