Not PIP, or Motorbility, but being retired, with numerous health complaints, and getting worse, I put an application in to the DWP, for Attendance Allowance. The form, was little more than a ticky-box job, with little space for any real, in depth explanation, just yes, or no answers, no maybes/sometimes, plus details of meds, doctors, and consultants.
They rang me, initially suggesting that I wouldn't qualify, based upon my answers in the form, but seemed sympathetic, keen to help nudge me 'past the post', with extra questioning over the phone. During the first call, one of my panic episodes developed, and I had to end the call. The supervisor rang some days later, and his questioning, and my answers, helped get me 'past the post.'
I had been in touch with 'Help the Aged' previously, inquiring about the process, and whether I might qualify. I was warned by them, it's best to enlist their help in filling the form in, so I wouldn't under stress my health issues, but I decided to go it alone.