And your original point remains entirely wrong.
Cases (seven day average) bottomed out at 354, July 6th.
They rose over the next two months to 1833 on Sept 6th.
That's a roughly 5 fold increase. I'd say that was a pretty significant uptick!
Testing (7 day average again) over the same period only rose from 115,000 to 192,000, not remotely to the same degree. And you wouldn't expect a linear testing to positives either, of course.
The pandemic grew throughout last summer in the UK once restrictions were at their minimum. It's just a fact.
Numbers from ourworldindata, feel free to check it out.