The UK currently has 1,657,270 positive cases of COVID-19

[Ms. Toad]

38. Completely irrelevant -

You are still fixated on quantity - and quantity, alone, does not guarantee that those tested represent the population as a whole. See the lengthy explanation above.

To take your assmption to the extreme - that 7 million testing sample could have managed to catch every single positive case in the UK. If so, there would be a grand total of 178,128 cases in the UK, not roughly 10 times that many, as you claim.

Until you know the mix of people tested (why they were tested, and the positive rate for sub-groups of people tested for that reason), you simply cannot, with statistical validity, use a large sample as a representative one simply because it is large.

You have numerous people in this thread telling you exactly the same thing. You might want to do some research on how to construct a valid sample group, rather than just searching for larger and larger testing quantities.