I think the UK have stopped letting people in entirely - but they were doing the mandatory quarantine period in hotels. The UK's done a pretty piss poor job at managing the virus, but they've done better than many other countries in a lot of ways as well. Which is actually pretty remarkable because our government is made up of pure incompetence bagged up and thrown into various people.
The fact the pandemic is as bad as it is currently is because governments acted very slow, imo. The outbreak had come to light right before the Chinese lunar new year - which is probably South East Asia's biggest tourism holiday. So as it was spreading from Wuhan to other parts of China - it was making its way around the world.
Once it hit Italy and we saw how badly places like Bergamo hit, Europe and the Americas could have acted much faster to contain the spread. Quite a few big countries really did not act anywhere near fast enough and tried to play it off like the pandemic spreading was normal and fine and it would all blow over after a few weeks.