763,
The UK tax rules are quite clear. If you are based in the UK you are working in the UK and you will have to pay UK tax. It does not matter what nationality you may be or where the company (Dragonair in this case) is headquartered.
I hope that is clear.
Furthermore yes you only pay 15% tax in Hong Kong, but you have to pay another 1.5% tax on top of that for your housing allowance (as a minimum - if you do not have to pay tax on the housing allowance amount itself) and you get no personal or family tax allowances at all. It is not PAYE so you get a large tax bill to be paid all at once.