How to Complain about the Assessor who did my PIP

I have been on DLA for about 10 years (Lower rate Care and Higher Rate Mobility). I finally received my dreaded letter several months ago about applying for PIP. I completed the form with the help of the B&W guides and went for my assessment in September. I received my decision letter last week and I have been awarded NOTHING and to make matters worse, was awarded ZERO points. Although I was half expecting it, it still came as a real shock. I have asked for a MR and intent to go to Appeal, but I also want to complain to the Independent Assessment Services about the assessor who conducted my PIP assessment, as the report is full of blatant untruths. How do I go about this?

Thanks