I wrote a detailed (4!)-page insert for my IB renewal form, using the guidance on this site, explaining exactly how my illness affects my life. I printed a copy and sent it to my GP with a covering letter.
I decided to approach this professionally and objectively, as a piece of work, closing my mind to the anxiety which was eating me inside. It helped to compartmentalise my conviction that my claim was right and my subjective but unhelpful fears and stress.
I realise you haven't had your renewal form yet, but if you can begin to put something accurate together now, you might save yourself a bit of stress at the time. It very much depends on what you personally would find helpful.
On the other hand, if you haven't had your renewal yet, and you know your GP is supportive, why get worked up at this stage anticipating how your review may or may not be? It seems very understandable but unnecessary worry and your GP will only be able to write as she sees at the time. And given that the spending review etc is still fluid, you may find things are different again in a little while. You've alerted your GP, so she'll be a bit more aware of relevant items in the press.
Best of luck.
