"Waiting times have left me in horrendous pain"

I have been suffering with back pain since December 2007. I was referred for physio for six weeks but this didn't help, so I was referred to Chesterfield Royal Hospital. I waited 7 weeks for a letter with my appointment and when I didn't receive it I rang them and was then told that they do not deal with back pain at Chesterfield and I would have to go back to my doctor. I did this and was referred for an MRI at Chesterfield in May, and then referred to the Hallamshire hospital in Sheffield. I have been waiting 9 weeks for that appointment, and this week received a letter saying "due to unforeseen circumstances" they had put my appointment back another 3 weeks. Not only is this putting my job at risk because i have been off sick since January, but the pain is horrendous (I have been diagnosed from the MRI with a prolapsed disc). Why are waiting times so long?