As you might be aware, you are entitled to amend misleading or inaccurate personal information that the DWP or the NHS holds on you, under the terms of the Data Protection Act: this is your legal right.
You can also request any records or data that they hold, to be released to you under the Freedom of Information Act 2000. Once again, this is your legal right. They are allowed 20 working days to respond, in practice the DWP always delay these requests. The FOI Act is more suited to non personal requests though.
It seems most doctors write misleading or inaccurate reports in relation to IB or DLA: wonder if those caring and trustworthy people at the DWP or Unum UK are behind this. All my recent medical reports look like I am looking at the report of someone else! I could not even be bothered to get them altered, as they do not impact on my current benefit, now or in the future.