Just to add a few things:
- The 15% tax on dividends only applies to US stocks, not any other stocks.
- UK taxes only applies if you are UK tax resident. If you are not UK tax resident, then you only have to concern yourself with HK taxes (of which there are no capital gains taxes).
- If you move back to the UK the present advice is to sell your assets first and then re-buy when you are back in the UK.