I would go back to your GP for advice first , seems like they are trying to rope you in. Chiropractors are still very much on the fringe of the medical industry , unlike Physiotherapists who have only really been accepted into the medical fraternity in the last 10 years. I have suffered from a bad back for a long time , I went through all the various scans and surgery etc.
I can say that Chiro or Physio is usually only a temporary measure, so after 12 months there is no guarantee that you will not revert back to your original condition.
Talk to your GP and try to find out how qualified your Chiro is , have you VHI to cover the treatment ?