If you live on your own (you do
), you're allowed to bubble with another household, which means you can have a friend around, or similar. But it must always be the same person. The friend can't bubble with anyone else, the friends' potential housemates cannot bubble with anyone else. This has tended to mean that a lot of bubbles cannot form.
https://www.gov.uk/guidance/making-a-support-bubble-with-another-household
There's also Christmas support bubble, but that's only now relevant to the population of England minus those that might bubble up with someone in tier 4 households, and it's only relevant for Christmas Day.