The pubs and restaurants do not allow mixed households indoors and those in higher tiers to dine and drink there.
Unfortunately the only way for restaurants and pubs to do this is to exlcude support bubbles from dining indoors so they can check ID, however otherwise there is no other way Imo. And support bubbles can still meet at home and dine outside.
I know so many people that have openly said that they have just declared a support bubble and people from tier 3 coming to oue tier 2 area, and now we are going to tier 3.
You can't stop mixing in private homes, but they should expect pubs to take some responsibility and simplify the task of doing so.