Any advice/personal experiences of PIP tribunals?

amy798

Hello, my mum lost her high rate mobility (and therefore her car) and high rate care in September, and has been housebound ever since she lost her car. She relies on other people to take her to the shops as she doesn’t have the money for taxi’s and cannot use buses as the vibrations and jolts give her pain as she has fibromyalgia, osteoarthritis, poly arthritis, audio-processing disorder, schuermann’s disease (curvature of the spine), depression and anxiety and a problem with swallowing food. I believe she has other conditions too but I cannot remember these. She cannot walk without crutches and has had to start using a wheelchair (which I push) to get her around places. She walks with a walking stick in the house, and struggles to bathe, dress herself, can only cook prepared meals, cannot budget finances correctly, she has urniary incontinence issues, forgets to take medication due to APD and fibromyalgia. She also struggles to remember many things and can no longer understand many words/ pieces of information due to APD. My mum has severe anxiety and struggles when meeting people, also because she fears people judge her on her disabilities, and cannot go anywhere unfamiliar unaccompanied. 
My mum has had to stop going to voluntary groups she used to help run which was for people with mental health issues, and she can no longer attend bible study groups nor church as she is a strong Christian. 
My mum’s tribunal is in two weeks, and I am accompanying her to it. We are both nervous wrecks as we do not know what will happen. The assessor last year lied an awful lot on her assessment notes that we received. 
Unfortunately my mum can not get a doctor’s letter as our doctor refuses this - he does not believe people should have to pay for these and flat out refuses to help. My mum also has a scrape and clean done on her knee many years ago at a different surgery - scans show my mum has only mild arthritis, however, after the surgery, they saw chronic arthritis that didn’t show on the scans and had to remove over half of her knee cap, however upon requesting this record it has apparently gotten lost and so have no evidence to back this claim up.
My mum has had thoughts of suicide because of being housebound and has said she feels as though these thoughts would be recurring if the tribunal was to go against her.
Is there any advice based upon this information provided on what to do etc?  
Please help. Thank you so much for reading. 
Amy