The UK has received and benefitted from waves of immigrants ever since the middle ages. In almost every case, they initially settled in the major cities, where the work was, in particular the East End of London. They naturally tend to congregate, as they can support each other. As time goes on, and they are better able to support themselves, they have spread out throughout the country.
A major exception to this was the wave of immigration from Eastern Europe after they joined the EU. Large numbers of them settled directly in depressed small towns, particularly in the east of England, taking work that workshy English weren't prepared to do (fruit picking, care workers, etc). These places saw immigration on a scale they had never seen before, and this was one of the drivers behind Brexit.
Immigrants benefit the economy, usually being hard-working and prepared to accept poor wages and living conditions that the indigenous population won't. However, the problems tend to come with the second generation, who naturally expect better.
In the case of the Hong Kongers, I doubt that many would come here. Unlike some previous immigrants, they are not being actively persecuted, they are not in fear of their lives. Hong Kong is prosperous, why move to a depressed part of the UK? You are unlikely to improve your standard of living. There may be a few idealists who would move, but the majority would see little practical incentive. And for those staying put, having a UK passport would be of little benefit, as I understand China refuses to recognise dual nationality.
