PIP appeal - waiting for a diagnosis?

Is there anyone who can tell me if when going through a PIP tribunal/appeal, they are allowed/can take into consideration the fact that I am on a waiting list for diagnosis (and have been for 2 years!).
I know for most illnesses/disabilities this might not be relevant, but it's to do with having ASD/Aspergers - which,if I do get confirmed, will mean I had it from birth.
Much of the PIP form is not so much about the actual label, but how things affect you/what you can or can't do, but I'm battling with them over the mobility part of planning and following journeys - for my diagnosed mental health problems I was given 4 points, yet I (and my gp and psychiatrist) feel I should qualify for the 'd' rather than 'b' -. I've explained the difficulties I have to the DWP over and over but they just come back with the arguement that 'd' applies to people with learning difficulties or ASD/autism.

My gp /psychiatrist wouldn't have referred me to go to the Autism diagnosis if they weren't fairly sure I had it - and just getting a label isn't going to suddenly change my ability to follow a route.

So is there a way I can argue that me being on the 2 year waiting list (nearly at the top now) should be taken into account for the mobility part of my PIP appeal?

thanks I hope that makes sense.
abby

thanks - they say that PIP is supposed to be about how things affect you, but it does feel like they like to have boxes to tick for diagnoses (even though they say they don't) - from their reasoning it feels like they would be more likely to accept my appeal to get 'd' rather than just 'b' if I had already got an official diagnosis of ASD - since that falls under the term of learning difficulty rather than mental health. It doens't change me or what I would do.

It's an appeal going to the Upper Tier so I'm trying to see if I can link it in to the error of law/failure to investigate.

I have requested a statement of reasons and record of proceedings but am yet to be sent it . If the tribunal followed the DWP assessment guide, rather than what is explicitly written (or not written) in the legislation then I thought that would come under the error of law? I'm hoping the SOR will also clarify why/how they came to their decision - if not I will be querrying that - my GP, Psych and the HCP all state that I would be unable to follow an unfamilar route alone, yet the tribunal still went for 'b'. I know I'm getting off the point but it just seems if you are able to state you have an offical diagnosis of ASD they are more prepared to accept you satisfy 'd' not just 'b'.