There are three parts to an assessment for a claim. The first is the opinion; what you have suffered, and your injuries all appear to be soft tissue sprains. The second is causation; had you not had the incident in question (termed the material incident) what injuries would you currently have? This second part sounds a bit of a nonsense but if you had a pre-existing injury that had been made worse that would have to be teased out. The third element is termed quantum; how much is fair compensation for the injuries suffered? All these are run through a Government agency called Medco which is a sausage machine for this sort of injury, and your report was created by pressing a few buttons and the template churns out. I have to say that £520 sounds pretty low to me; it's not much more than the person assessing you would have received.
These reports are normally done at 4 to 6 months after the event.
The pertinent questions now to ask are:
1. Howe long is it since the injury now?
2. How much have things settled?
3. Has anything else appeared since the assessment?