recovery of overpayment before the appeal is heard

I think this has been discussed a few times before but I haven’t come across this for a while: how do you prevent the DWP and local authority from recovering an overpayment of benefit before the appeal has been heard, and get back any deductions they made prematurely?
My client found work after being unemployed three years ago. He claimed extended HB. Three months after he started work his local authority wrote to him to say they’d overpaid him HB by one week. There was a dispute about the dates, as well as about whether the overpayment was recoverable. The dates the local authority put on their letter suggested that, rather than overpaying him by one week, they still owed him three weeks extended housing benefit. He refused to pay the alleged one week overpayment but didn’t appeal. A few months after that he moved house to be nearer his job (to south Liverpool, which is my area). He was made redundant again at the start of this year. When he went on to income-based JSA after six months, he got a letter from the DWP Debt department in MItcheldean saying that his “local authority” (his previous one) had asked them to collect an overpayment of housing benefit from him. This was the disputed one week’s overpayment. He appealed this time, but the debt centre started taking deductions from his JSA three weeks after sending the overpayment recovery letter, that is, before the deadline for him to appeal was up. They continued the deductions despite demands to stop, and have still not acknowledged the appeal. However, he did get a letter from the original local authority (Rochdale) complaining that the DWP debt centre had told them that he had appealed, and insisting that their original decison was right - so it seems the debt centre did get his appeal. My reply to Rochdale was that, in pursuing this minor debt nearly three years on, they had opened the client’s right to appeal again and he was exercising the right; and we would like to see appeal papers in due course.

However, the client really wants to know how he can get his deducted benefits paid back. I haven’t come aqcross the DWP making premature overpayment deductions for some time and the only way I know of tackling it is by threatening judicial review. That stopped the DWP making ongoing deductions, but in this case they have already taken the entire amount of the disputed overpayment (it was only £80). All I’m finding in the sources I’ve looked at is that if a claimant agrees to repay an overpayment before their appeal is heard, there is no method of claiming the money back if they win the appeal. In this case, the cliamant didn’t ‘agree’ to repay, but I can’t find anything else relevant to the circumstances.