IO540 i along the right lines. Of course it does vary from country to country, but certainly I used to fly G-reg a/c here on an American licence. Could not take them out of the country though. The UK licence (& by continuation I hope, the JAA licence) is highly respected & even if you need a local licence it's usually only a paper exercise.
The HK authority is the Civil Aviation Department which you should be able to google.
Good luck!