If I remember right when I went to appeal tribunal their decision is more or less final and the only way to over turn any outcome of an appeal is if there’s a misunderstanding of a point of law that’s never been tested before at a tribunal court.
I had a trainee solicitor at my tribunal but won my case in court so the subject of point of law was mentioned to me as a way forward should I of lost my case and having won it, it was never ever mentioned again so can’t help and I’m sorry for being so vague.
For some good advise try putting this question over on https://youreable.livingmadeeasy.org.uk in the “benefits help and advice” forum and lookout for a forum member under the name of “nukecad” who knows a lot about how disable benefits works and points of law.