I came across this explanation, which may be useful:
What is Disability Living Allowance for Mobility?
This can help when you have difficulties walking outside your home. Your difficulties could be due to physical or mental health problems. The rate you are awarded depends upon the kind of mobility difficulties you have.
What is the lower rate?
You can claim the lower rate if you can walk, but need someone with you when you go out to help you find your way about. For example: you have problems seeing, you have panic attacks, you have a mental health problem that makes it hard for you to cope when you are outside, or you have learning difficulties. The test looks at whether you can manage on your own in unfamiliar routes. So, if you can follow routes that are familiar to you, it doesn't matter. This sort of walking will be ignored and you may still qualify if you cannot cope with routes that are new to you.
What is the higher rate?
You can claim the higher rate of Disability Living Allowance for Mobility if:
* You are severely mentally impaired with severe behavioural problems and you get the highest rate of Disability Living Allowance for Care, or
* The effort of walking would be a serious risk to your health, or
* You have no legs or feet, or
* You are deaf and blind, or
* You are unable to walk at all, or
* You are 'virtually' unable to walk.
What does 'virtually' unable to walk mean?
This is where, for example, you get breathless or tired out after a short distance, your walking is very slow difficult or painful, or your walking is interrupted so much by stopping that you make very little progress. The time taken to walk, the distance you can walk, how you walk and the speed at which you walk are all taken into account. You have to show that your problems have a physical cause.
And yes, both Age Concern and the CAB can offer help. They willlikely have people who are experts in filling out these claims, and they will know exactly what is relevent and what is not and are also likely to think of many things to put on the form that you won't have, because you thought they didn't matter or were obvious...etc.