52 week rule for hospital patients

My client was admitted to hospital on 12/6/15 and remains an in-patient.

Housing Benefit has remained in payment since his admission on his private tenancy. He went awol 29/1/16 – 3/2/16 but then the next period of overnight leave was not until 13/7/17. Since then he has had several other periods of overnight leave - the last being 26/8/17 to 16/10/17.

It has been assumed that housing benefit has stayed in payment because of periods of overnight leave in the last 52 weeks but now having looked back at his overnight leave history to get back payments due for PIP and ESA it is fairly clear that hb should have stopped 3/2/17 and has, I suspect, only continued because the Benefits Unit do not know that he is in hospital.

He is a psychiatric patient so am hoping may be scope for challenging the recovery on these grounds but just wanted to check that I am right in thinking that any overpayment will only be from 3/3/17 - 14/7/17 i.e. the date after his next overnight leave since he would then anyway have become entitled again to housing benefit for another 52 weeks after this date.