Under the DDA and the DEA employers are not allowed to discriminate against someone on the basis of disability. They also have to consider making 'reasonable adjustment' to enable someone with a disabiltiy to be able to do the job. The bigger the employer, the bigger the adjustment is considered 'reasonable'. For example, they might be able to offer you a different type of job that you can do e.g. office-based rather than driving. However, in the event that you are not fit to do the job you are employed to do, and 'reasonable adjustment' has been considered and rejected or has not worked, they can dismiss you on the grounds that you cannot fulfill the job for which you are contracted. Sorry.
Smidge