I am new to this and hope my experience will help.
I have recently had my bus licence suspended for 12 months as I have just started on insulin for my diabetes. I am the first driver in our company to do this. I gave my employer notice that I would be going onto insulin and so far they have been very supportive. I am on sick pay at the present time and the company are trying to find me alternative work until I am able to reapply for my licence next year. My GP will shortly be signing me as fit for work. Until my employer finds me alternative work then they will continue to pay sick pay, however, due to my short time at the company this will revert to SSP at the end of May (that will be painful).
With the support of my Union rep, employer and GP hopefully this should work out.
You cannot be dismissed now for being on insulin and your employer must try to find you a reasonable alternative whilst you are unable to drive a bus.
Good luck.