Well done for finding those reports. I note their dates (Guardian 29 Apr and iNews 19 Apr). I can't help guessing that the increase in numbers over those weeks was in good part caused by UK residents returning from visits to India (reason??) and testing positive after flying in, including the surge of arrivals in the 4 days before the air link went 'red' and enforced hotel quarantine was imposed. So we might expect the rate of increase not to be maintained though community transmission. As a VUI 'outbreaks' are not yet subject to surge testing aiui.
I sincerely hope every individual flying in self-quarantined 'at home' for ten days.
@mjr has pointed out the reasons why people don't self-isolate, but presumably if you can afford a return air ticket to India, you can afford to self-isolate on return if required.