Hi Jak
There is a thread think its called disability benefits which may be of help to you.
Have a read through, as you cant get DLA for diabetes, but you can for complications associated with diabetes.
To be eligable for a mobility car, you have to get the higher rate of the mobility component for 3 continuous years if you lease the car, or for 2 years if you want to buy a second hand car on the scheme there are conditions for buy second hand though, it used to be car has to be under 4 yrs old and have less than 40,000 on the clock, not sure what it is now but you can check on the mobility websties.
It is quite a difficult and daunting process applying for DLA, so shout if i can help
Juliexx