Jon
I don't know where you live, but I strongly recommend you consult Dr Ian Perry in London before you do anything else. He's a very experienced aviation medical examiner used by many professional pilots.
If you're way out of limits, nothing can be done. However, if you're borderline, it's far better to be armed in advance because, once a CAA decision has been made, it's notoriously difficult to get it changed.
Link to Dr Perry
Tudor Owen