I worked as a volunteer Benefits Advisor with Age Concern for 10 years and supported and accompanied DLA and Attendance Allowance apellants to many Tribunal Appeals. From my memory the success rate was considerably more than 40 %.
DLA and AA forms are scored like credit rating reports, get above a certain score, you get the benefit, get below it and you dont,. Because the forms are scored by medical unqualified and fairly low grade staff my experience was the simpler your disability the easier it was to get the benefit. As soon as claimants had multiple disabilities and complicated medical conditions the staff scoring it didnt understand either the illnesses or the disability and seemed to just refuse benefit.
Although the word 'Tribunal' sounds intimidating the procedure is not. The three people on the tribunal panel and the claimant and whoever is with them. sit round a table in a small room. The panel members ask you about your condition and how it affects you, it is not confrontational nor an inquisition. They are seeking information. On several occasions the Doctor on the panel actually understood the disabillity problems my claimant's medical conditions caused better than their GP.
Always take someone with you, from a Disability Rights group or a friend or member of your family who knows a lot about your problems. It is easy to forget things in a tribunal and to have someone beside you who if you are answering a question and leave something out can turn and say to you 'Remember when....' so that you can then say more is really useful.
Always write to your doctor asking for a letter about your condition. Say specifically what information you need. For example 'I said that I am afraid to leave the house alone because my diabetes is unstable and I am afraid I might have a blackout'. He can then confirm that your diabetes is unstable and that you have lost confidence etc. The form sent to your GP by the DWP focusses very narrowly on physical disability, which would not cover an example like the one above.
Most of the people I attended Appeals with said afterwards how nice and friendly the panel were and how unintimidating the experience had been.