Nearly all income estimates for Uber drivers (both in the UK and elsewhere) are off-base, if only because obtaining pay stub data is all but impossible. Uber certainly doesn't hand it over, nor are its drivers required to do so.
Regardless, the 'best guesstimates' typically fail to take into account the surge pricing that serves as the main reason drivers work for them. £40/hour isn't uncommon on weekends when the Tube stops running and pissed wankers want to get home and pass out as quickly as possible.