The whole Hong Kong scenario always seemed weird, utterly reminiscent of backroom negotiations and colonialism.
HK's retrocession to China was the right thing to do.
Unfortunately it seems that it is very hard for Britain to get over its lost Empire. They should really move on.
Maybe, it should go to China, but why not have a referendum, it's cheaper than war -- and it makes a stronger argument too :)
The problem is states competing against each other and they know that HK is a way to create trouble for China.
But if the UK had called one, it might have been different.
We've successful solved territorial disputed with referendums in Europe. We just rarely talk about it, because there was no war to talk about :)
How things change.