Hi JB:
I live on Cheung Chau, so can perhaps help w contacts for flats.
Some time ago, I did small website for a holiday flat owner here (dunno about prices now; think the email may no longer work but not sure):
http://hkseaview.tripod.com/
Fung Wong Holiday Bungalows on Lantau a good place, but in Tong Fuk, so fairly remote; some info if you search this forum.
Hope this may be of some use.
Martin