Do you know what is in your occupational health? Could there be a memo. a letter or some handwritten notes that show that the force did not act within their lawful duty when they made the decision to retire you?
It is foolhardy to attend a review they have instigated upon you without knowing what information they have on you beforehand. A Subject Access Request (SAR) under the Data Protection Act is a method to get full disclosure of personnel records and occupational health files and should be the first action if ever called to a review of your injury on duty award
Once submitted with a form of identification (such as a photocopy of a passport) and a £10 cheque, you should receive within 40 days the required information. Then you will not be entering the process blind. Indeed there may be something within the file that indicates that any previous decisions were unsound.
A template letter can be found here:
There is nothing stopping you from putting in a SAR once notified they are starting a review process and then another SAR once the review has completed. The second request should specify all handwritten notes made by SMP during the assessment.
You might also discover that they have destroyed your personnel file under some internal retention policy. If so it can be argued how they are going to compare your skill set when they have no record of what skills you gained during your service.