Funny giving advice about leaving;-)
Go on a base first. If you have done say 3 years, you will get 30% of your PF tax free and then the remaining 70% will be subject to HKG tax(just came down to 15% I think?). If you resign whilst HKG based you will only get the 30% for 3 years service, or as applicable to your years of service.
Unless you are in your first year, you must give 3 months notice or payment in lieu. I think many people have found themselves too stressed to fly after resigning and have dr's note accordingly. According to HKG ordinance they cannot fire you whilst you are on sick leave. Besides, it would be a little redundant for CX to fire you when you are in the last 3 months anyway.
Tax in HKG is called provisional but is in fact more like PAYE tax in australia. You will never pay tax for income you haven't earnt. So when it came to paying 'provisional' tax in early Jan07, you were in fact paying tax for the 9months from 1/4/06-31/12/06....ie 75% of your likely annual tax bill.
CX are required to withhold paying your last salary/salaries until you have IRD clearance. If you think your tax bill is greater than 3months salary you are doing something different to me.
Clear as mud?