HI there,
I'm T1 (and obviously on insulin). I lost my category D and D1 on diagnosis. I have heard that 'non-voluntary' ambulance drivers can keep their C1 licence (to note: C1 needed to drive ambulances - people on insulin can apply for a C1 if diabetes 'well-controlled'.) if diagnosed as insulin-dependent. On the other hand, I've been banned from driving buses and mini-buses - anything over 9 seats, I think. Anything which involves carrying others....
You might find, since you're already in the role, if you can prove you can control your diabetes, you may be allowed to continue. Its a grey area.
If you can't continue your role, welcome to the club......if you're on insulin you're branded as a danger on the roads, regardless.