For those of us in London, the majority of local hospitals do not have a Diabetic and Endocrine department, and we are required to use those of other hospitals. As I understand it, for well controlled, balanced diabetics, especially T2s, the NHS preference is to have them handled by their GP.
For those of us who are T1 in London, we are referred to the clinics at one of the hospitals. There are three that I could have been referred to and I use the one nearest where I work. I believe that the same is true in other parts of the country.