(2-part post):
Very few countries use the 'PAL I' broadcasting system (which is used in the UK) but, fortunately, one of them is Hong Kong.
Source:
http://kropla.com/tv.htm
The electrical supply in the UK is 230V with a frequency of 50Hz. The supply in Hong Kong is 220V, 50Hz. Most electrical equipment is usually labelled as '220V/230V' so it's likely that TV's should be compatible. (Just make sure you check the label on the set).
Source:
http://kropla.com/electric2.htm
So, apart from having to change the plug, it's likely that any TV set purchased in Hong Kong would work in the UK.
Another factor, however, which needs to be checked, as far as terrestrial reception is concerned, is whether the same group of frequencies are used in each country (otherwise the tuner wouldn't be able to pick up the signals). Once again, it seems that there are no problems because Hong Kong and the UK share the same frequency allocation.
Source:
http://en.wikipedia.org/wiki/Television_channe l_frequencies
Sky boxes work by using their own tuner and feeding an AV signal, via a Scart lead, into the TV. In effect, the TV is simply being used as a monitor. So, because the tuner doesn't form part of the TV, there's no reason why a set purchased in Hong Kong shouldn't be able to work with a Sky box.