Hello and welcome to the forum. Glad you found us and posted here.
I'm not certain what kind of evidence is required in this situation but you have covered the two most obvious sources. Do you live with your parents? Perhaps they could offer some personal evidence about your depression. Perhaps a letter from your lecturer, tutor or course co-ordinator.
I suggest you contact the department concerned in making these approvals and ask them what they need. I suspect they have a standard list of sources in these sorts of cases and will be able to advise you on the best course of action. Usually they are very helpful and will tell you how best to go about getting this post census remission of debt. Sounds as though it will save you a reasonable sum of money so it is important to get the approval.
Find the phone number or get someone to find the number then I suggest you make contact. It's always better coming from the person concerned and shows you are a genuine applicant. It also gives you the opportunity to ask questions about any information or advice you are given. Remember to have a pen and paper handy to write notes. It's amazing what we forget two minutes after a conversation.
I send my best wishes to you in managing this. Not always easy but you do have a good motive to work through this. Please keep in touch and tell us how you are going.