Never gotten the feeling that they want to secede from the mainland, what they want (at least in HK's case) is for democracy to be preserved. The "1 Country, 2 Systems" policy seems to have worked fine for them so far, there's been some unhappiness recently I think though as apparently Beijing are trying to get their grimy hands into HK politics.
I always got the impression from when I was in HK and speaking to people, especially the younger generation (twenties etc) that given the choice they would rather still be under British rule as opposed to Chinese rule