PIP F2F assessment

Sorry about this. I am getting seriously frustrated and anoyed with independant assessment services. I have been told I need a face to face assessment to remain on PIP. The first assessment was cancled due to the assessor having a family berievement. I attended a second one but the assessor aborted the assessment and called an ambulance for me. I recieved a further appointment for which I attended to find out that it was incorrect and they shouldent have sent it out and they had no way of seeing me. I attended one further appointment aranged on my day off as the others I had taken anual leave at short notice. I was finally assessed but wasn't impressed with it, they didn't ask a number of questions that I was asked in the past and tried to say one of my conditions wasn't on the form despite it being mentioned neumerous times in the form a couple of years ago. I recieved a letter today to attend another assessment so rang independant assessment services who told me that there was not enough information in the health professionals report and I needed to be assessed again. I have rearanged this assessment for a time that is convenient with me. I am also going to ring the DWP tomorrow and ask for a Subject access request.
Is there anything else I can do to improve things?
I hope my next assessment on Monday goes ok and it is finally sorted. I also have to go to a different area and assessment center so don't know where it is. I am going to do a dummy run to find out where it is. Sorry about the long post and moan.

Thanks for that Gordon it is really appreciated.