I’ve not logged in here for ages, but I wanted to reply to your post Northwind – there’s several things I can point that DWP have some wrongly there.
Your savings – if you’ve spent them to repay debts, then they can’t say that you did it to increase your UC award (called intentionally depriving yourself) the UC rules specifically state that you can repay debts, even if they don’t have to be repaid immediately
Also, if you had problems with the ID verification, that happens after you make your claim. I’d you’ve made the claim, they must have made a decision that you were not entitled to UC. You can ask them to reconsider this and award from the earlier claim date, especially as it doesn’t seem to be your fault.
Worth also telling them about your mental health problems and perhaps getting a medical certificate/fit note from your GP as well, even it is is to just make things easier