I believe the one great problem with the FoIA is that, even if the information is supplied, it does not have to be accurate.
You will receive a letter saying you can complain if what you receive contains;
1. Errors of Fact
2. Subjective Comments
3. Opinion or comment based on factually incorrect information
However, the Information Commisioner will not support you if the holder of the information refuses to correct it, even if you can produce irrefutable evidence it is incorrect. They regard their job done when the information is provided. It is up to you to take proceedings, which few can afford against a Department of State.
A word of warning. If you enter into private correspondence with the ICO, be aware they will routinely pass copies of your correspondence to MoD.