As the deadline in Thursday, then there is a chance you might not make it. If thats the case you need to speak to your tutor, but also some sort of counselor or your GP. Ideally you should see them before, so they cna confirm your anxiety and depression have still not improved. If you have their support, then that would make it easier for your tutor as it would show it was still serious and a third party professional had confirmed what you were telling them.
Would an extension realistically work for you?
Rather than think of quitting, then maybe deferring and returning when you have it under control would be a better option.
Dont worry about the money, they wont ask you to start making repayments till you are earning £21k plus.
Do try and book some appointments to see people though, it will relieve some stress that you are doing soemthing. If you are unable to then phone a friend or your parents and ask them to help. Your mental health and overall well being is more important.