£7.83 is The UK hourly rate National Minimum Wage April 2018 to April 2019. Please note, that this figure is due to rise to £8.21 in April 2019.
[ [05:54 03/12/2018] ref:
https://www.gov.uk/national-minimum-wage-rates]
Estimated Housing Benfit overpayment calculations based on figures published on Wikipedia
[ [05:53 03/12/2018] ref:
Wikipedia: Housing Benefit]