Transdev Trainee Train Driver interview questions

Online test, psychomotor testing, interview, Medical. Everything went well until the medical because im taking insulin for diabetes, I advised that im diabetic in my interview and was still put through to medical so thought my chances were good, very frustrating to be advised that because im taking insulin that i can not be a train driver, the most frustrating part about it is finding out if I wasn't taking insulin that id likely be fine, as i was told by the medical practitioner i saw at the time ( I had only started insulin 2 weeks before the medical ). I wish when i bought up that im diabetic in the interview that i was questioned about it as then i wasn't taking insulin and would have looked at other alternatives, which i now am and are working well. This is a job i have wanted for years and there is not any information i can easily find about the medical requirements for the job. Frustrating to lose an opportunity of a life time because of this.