My brother has been for the courses organised by British Council in HK. So far I know from him, it's not good as he expected.
well, the best way to learn could be going aboard cos you seldom have a chance to speak in English in Hong Kong. Even you know from lesson, many of the time, you don't use the colloqual English. for example, we learnt from books that after you say, "thank you", the next sentence should be "you are welcome". That's how people from England sounds. In terms of Aussie, they would say "No worries", "Not a problem". That's an example for something that you will never learn on books or lessons.
Another example is no matter from which countries, they would say "Good monring. How are you?". It's not just "Good morning" and finished.Besides, remember names of people is very important. this is kind of respect. that's part of the culture.
Maybe you can consider short courses, say 1-2 months to go overseas and try to speak more.
Learning a language is not just the volcaburies or words but the culture as well.That's why it's very difficult to improve English under the local Hong Kong environment.