Hi Oops...Daniel.
As I understand it from previous posters and questions asked here, the Oil industry is rightly very tough on medical standards. Presumably your control was good enough previously to get the job, therefore I think you need to focus on what is causing the hypo's ? The problem !
As for help, are you in a Union ? There is also the Disability Discrimination Act, but they really are only obliged to make 'reasonable' adjustments to accomodate your Disability in the workplace. You want to find out exactly what is going to be discussed, take a 'friend' in with you and make copious notes. Do not agree to anything before taking advice, maybe from the CAB, (Citizen's Advice Bureau).