Would the British public accept an additional 3 million Hong Kong immigrants?

We would find it hard but no-one expects that number anyway.

Besides, I doubt very much the Chinese Government would allow many of them to leave, not just because that Government is an inhumane bully, but also because doing so would admit fault or error on its part.

I would! But realistically 3 million people aren’t gonna move if china even lets them 👀 maybe it would end up being about 50000 at most and we can definitely handle that

Will the Chinese government allow any of them to leave?

That’s what the government have signed up for ...

I doubt it