Let me put it like this. Imagine I'm an alcoholic, but I can't afford rehab, so I steal the money to check myself in. I get better and everyone in the world agrees that my new state of sobriety is the best possible outcome for me. However the police find out, I go to court, get a big fine, get depressed and start drinking again. I ask for help from my friends, but I neglect to tell them about actually what happened, I allow them to entertain the idea that I am a total victim.
My point is that we need to know that context of a situation, or we can't truly help.
So I have to strongly disagree with you that history has nothing to do with Britain's current stance on HK. Britain is a sad, humiliated, crumbling nation. Brexit is in fact Britain's chickens coming home to roost from the very events of which HK is but one in a myriad of aggressive wounds on the world. Those rich, Eaton-educated families that got their wealth and arrogance through the authoritarian, totalitarian, anti-democratic practices of colonialism are finally beginning to find their true place in the world. Either Brexit happens and Britain suffers Northern Irish violence and Scottish independence, or Brexit is cancelled leading to the collapse of the Conservatives. Either way the core source of British "pride" has a very sobering journey ahead of it.
Hate to break it to you, but the rich elite in the UK will not suffer because of Brexit. The poor will suffer, as they have always done. The elite will be just fine, and probably be in a position to strengthen their standings from the chaos.
And finally, what is your conclusion on China then? You are not arguing they're in the right, so what? What's your suggestion? What's your take? What should the CCP be doing right now? Should they be implementing democratic reform on the mainland to converge with the HK culture more?