There was 1.2 million tests taken that day in the UK. Maybe I am reading the website incorrectly but if you test more you are likely to find more
https://coronavirus.data.gov.uk/details/testing
Its a daft format and in reality nobody would really want mass transit of people,vaccinated or not. Its very difficult for the EU countries as freedom of movement is such a right that restricting it is difficult for them and much easier to do it to the non EU countries, especially the little unimportant ones.
Anyway its ok as long as you are not in the country for longer than 12 hours as the virus doesn't bother you then