Here is your thread from the intro page
http://www.felinediabetes.com/FDMB/threads/just-diagnosed.214781/
If you have had diabetic cats before, you will know the general routine. Did you use Lantus before or was it one of the faster acting insulins?
Maurice is a heavy cat at 8.6 kgs. Is he a big cat or is he over weight?
I'm sorry you have the diagnosis of cardiomyopathy and poor kidney function. Did they say what stage kidney failure he had. Probably best not to give fancy feast canned food as it has a high phosphorus level which Maurice does not need with kidney issues.
I used Weruva 'cats in the kitchen' canned food for Sheba before I transitioned to home made diet. It was lower in phosphorus.
You mentioned you were stopping the beef mince....why was that? It should be fine to give. Is it the mince you buy from the supermarket (human grade) or pet mince?
What type of cats do you breed?
It is possible that the one high number of 40 was from the stress of the untreated cardiomyopathy and from the vet visit. Was that the only high number they recorded before they gave the insulin?
It is possible the extra drinking was from the kidney issues, not FD.
Are you able to get a copy of the blood test results from the vet? If you post them we have someone who can tell you lots about them.