Hi Sleepdodger
Assume you mean HK$650k pa, so around HK$50k pcm (post tax- 15% flat). I agree with Laptop that it'll be tight for a family. You won't be living the "typical" expat experience on that, largely due to cripplingly high rents (although your allowance might cover it depending on what you go for). However, the "typical" expats are becoming less typical and there are increasing numbers of westerners here without the whistles and bells packages of yore, and increasing numbers of westerners living in Kowloon and the new Territories, which are cheaper. Harbour City is in Kowloon, so if you were okay to live over there, rather than the island, that would save you some money. My sister lives at Prince Edward MTR- 500sq ft 2 bed in a local building, and pays HK$10k per month.
Re nurseries, just to clarify, nurseries like you have in the UK that open from 7am to 6pm and provide all day, 5 day a week care, basically don't exist. Most expat kids go to private pre-schools half days from age 3 (some do full days but it's rare), and maybe 2/3 half days from age 2, but FT "wrap around" daycare is aimed at low income local families and you wouldn't qualify. In terms of FT childcare, most people who work (and many who don't) have a helper, usually Filipino or indonesian, who lives in and looks after the children/does the housework etc. Min wage (incl food) is c HK$4.5k per month). My son is 23 mo now, and to give you an idea of his schedule, he goes to pre-school 2 afternoons a week and then does various other stuff like Gymboree music, mini soccer, gym class and then some helper play dates in our building. I work 3 days a week, so my helper takes him to most of these classes. Bear in mind that helpers have no formal childcare qualifications, so it's a very different model to the UK. However, it's also very affordable.
HTH