Hang on in there buddie..... I was in the same position too (london, looking for a job in IT without a work visa, applying through jobsdb).
Unfortunately I dont have the miracle answer other than you have to work twice as hard to convince an employer on the phone why they (a) should hire you and (b) should sponsor you for a work visa.
There are obvious things you should do such as:
1. highlight that you are a native english speaker.
2. Be keen, I mean extra keen (think you are in America [no offense if you are American!], and really sell your ass off)
3. follow up all applications with a phone call/email (this helps a lot) -Remember when you send your CV it ends up in some school leavers inbox who has to read it and file (no prizes for guessing where it ends up!).
4. Work out which companies specialise in your area of IT and target them heavily (ie check the website out, get to know the names of key stakeholders, start calling people up etc.).
Also you must keep in mind that with any employment its a two way street so you have to make it a worthwhile proposition for them which inevitably means you will take a salary cut Also bear in mind that Hong Kong is predominatly a front office financial gateway for China. Middle and back office operations tend to be housed in India, Taiwan, China and Singapore.
Failing that attach a picture of brad pitt/angelina jolie to your CV
Good luck.... If you are still getting knowwhere in a few weeks time, PM me, and I will try to dig up some more info for you.