Who ever said anything about living in Central London? I for one would not want to, Cambridge, Bath, Bristol, Reading, Brighton. Unlike Hong Kong there are many places that are nice to live in the UK and still close enough to LHR.
Yes you can survive in Hong Kong on this package but it really is not worth it as everyone will prove when they start leaving after they have 1000 hrs in a jet. This will do one of two things. Push out SO time to the absolute max or increase your package once more. It is not JUST about a house and buying food. It is about living in your home country with your long time friends, close to family, close to the things you enjoy. Hong Kong is OK but it is not my home and I know for a fact that this package is not enough for someone to leave their home for, be it saving potential, standard of living, or any other number of arguments.
This is not enough money for an expat widebody pilot to live in Hong Kong. It is enough for a single cadet with no flying experience or maybe someone with no jet time trying to move up the ladder. Once these people become widebody pilots they will know by then that this is not enough and they can find better opportunities elsewhere.