You can still drive a 7.5T as you have "grandfather" rights. However, you will have to have a yearly medical and complete the questionnaire. You will also have to demonstrate you have been testing your blood sugars, every day and at least twice a day, over the last 3 months (don't quote me, please check with DVLA). I got my Class C1 back so I could drive a horsebox but on renewal was turned down due to not demonstrating enough testing. I argued that as I wasn't a professional driver why was this needed and also what happened regarding holidays etc. Anyway I didn't win :-( and gave up, I only ever used it half a dozen times.
You have to demonstrate you are testing and your are aware of any hypos etc.
I also have a bike licence so just make sure I test and carry a mars bar with me, just in case. Your insurance premium shouldn't increase overly.
Good luck