I don't know much about supply work here. Others could advise you more about that aspect. There are also language schools that hire on part time basis, which will get you into the swing of things.
But with your experience and qualifications, you may want to look at full time employment, either at international schools, which advertise in the papers (I think ESF have their own recruiting process), or on the government NET scheme.
With international schools, you would be teaching under similar conditions as the UK, ie, a full and varied workload and most schools follow the IB curriculum.
On the NET scheme, especially in primary schools, you would only have about a third of the workload that you do in the UK and you solely teach English language or Literacy. The bonus is, you generally work with much nicer, better behaved kids. Of course, there are other problems that offset the good points (the way things are done here, isolation, sometimes you feel that you are not a real teacher and lose independence.) Both pay similar salaries.
The NET scheme is pretty much all year recruitment so if you get your application in, you may be in time for this year's recruitment. The schools that need NETs are looking at CVs now. However, these positions are highly sought after as the NET scheme can be a cushy number if you get a good school. Quite a few teachers would be reluctant to go back into full time teaching when they go home. Also, bear in mind that Schools that are recruiting have NETs who are leaving or being pushed out for various reasons, good and bad.
Finally, you'll have to think about your UK teachers pension. Continuing to contribute whilst here can be costly over the years.
For the NET scheme, you can ask questions either on www.nesta.com (mostly secondary positions) or HKPNETs Forum - Index for primary advice.
I nearly forgot, the only professional qualification the NET scheme insists you have or get, is a TEFL certificate. Yes, it even over rides a PGCE!