Welcome to the forum Solenn, he will lose his Housing Benefit, but if you are working that amount of hours you will be much better off unless your benefit exceeds the amount you would earn. When I had Housing Benefit in 2012 my amount was approx £400 per month and when my wife started working her hours were 27 hours per week at £6.31 per hour and we are better off without the Housing Benefit.
Congratulations on finding a job!
