Oh, yes, I saw that thread. didn't know the outcome (or that it has gone bonkers).
So, facts aren't in dispute: He was engaged to do X hours on the Sunday, Didn't do those hours, was caught out, dismissed.
Mitigating circs being (IIRC) that he hurt his ankle and couldn't work because of this and went home to rest it.
They will no doubt have said he should have phoned to tell them, should have reported first thing, should have asked to fill in accident form, etc, etc, but didn't do any of these until after he was caught.
From their point of view they have no way of verifying if anything your DH says is correct or not, but that if it were correct he could have done things differently.
Given the facts, I think the process itself is by the by. The facts themselves aren't in dispute. On what grounds is he appealing? Is he appealing because the dismissal is out of proportion to the offence, or because his H&S were compromised by the conditions and therefore he was unable to fulfil his contractual obligations because of this? Or for some other reason?
Because of the H&S angle it isn't straightforward, and I think you probably need the advice of a specialist lawyer here, and I think you should go see one on Monday. Do you have any evidence to prove he was injured on the Sunday?
I think TBH it would be a red herring to complain about the process itself. Is the same person hearing the appeal or has it gone further up the chain?
Also - how long has he worked there?