How start with a mandatory reconsideration letter

Hi everyone, I had my f2f for pip on the 12th August, finally plucked up the courage to ring for the assessment report last Monday and received it on Thursday, I've been awarded 0 Points for anything, which came as no great surprise to me, the same as my changeover from dla to pip 3 years ago which went all the way to tribunal.
So as I have the assessment report I'm still currently waiting for my decision letter to deny me of a pip award, I thought I would start preparing a mandatory reconsideration, but I'm at a complete loss as to where to start.
How should I begin my letter?
Should I suggest the descriptor I believe I should've have scored?
And then go on to explain my reasoning for this?
On the report it continuely states I've have good insight to my mental health diagnosis should I address this explaining I've been living with this condition for 18years? So its no great surprise that I know what my condition is?
It also states about me not have any mental health input, which is true, but that is because on and off for the last 18 years I've received counselling, psychotherapy, group therapy, one 2 one therapy, exposure therapy, and after the last bout of group therapy my gp decided to give me a break from it as it was not having much affect on me, and she has set up a community hub with other Dr's etc that runs one a month which I can access whenever I feel I can manage it and I also have open access to mental health services in my area where I can self refer to.
Should I try to see my gp to see what she thinks in respect to the pip descriptors I believe I qualify under and see if see can give a more detailed report to add to my mandatory reconsideration?
I'm really sorry for the long winded post and asking so many questions, but I really want to have a good strong mandatory reconsideration and the best possible success, before I have to ready myself for a possible tribunal again. I really appreciate any help or advice from anybody who has gone through this.

Thank you Gordon for your reply, yes I am on the very highest dose available for my prescribed medication for my depression, anxiety, ptsd, agoraphobia, social anxiety, insomnia etc, the assessor has gone down the route of I choose not to do things rather than can't do things, she seemed very fixated on the fact that I understood my illneses, mental health, a rare illness called solar urticaria and osteoarthritis, which isn't completely true, as she was made well aware that my diagnosis of osteoarthritis was waiting on xray results, but my gp was pretty certain it was, which was confirmed about a week after my f2f.
Do you think I should try and see my doctor to see what her input could be for the mandatory reconsideration, as she is the person who knows me the best and is the one making decisions on what to do with me regarding treatment?