As you know there isn't much activity in light aircraft aviation in
Hong Kong apart from the few aircraft in the Hong Kong Aviation Club. A
friend built an aircraft in his apartment in Hong Kong but shipped it
home to Australia for final assembly and test flight. Suggest you join
the U.K. Popular Flying Association if you're interested in homebuilt
aircraft. You can make many friends and contacts through the PFA and
they have some members in Hong Kong. I believe there is an agent for
'Airborne' trikes (powered hanggliders) in Hong Kong - see
http://www.airborne.com.au/pages/home_n.cfm - and that may be the best
way to fly in your limited airspace.
Cheers,
Joe