simon find a good driving instrucer im now 40 i only passed my test about 4year ago if i can do it im sure you can too, i failed my first test and stopped my theroy test ran out i left it for awhile then decided to try again, i went back to the same driving instructer, and managed to pass my theroy on the second try and passed my test on my forth try, i used an over the counter calmer, from the chemist it came in liquid form and you can either add it to water and drink it or use the dropper and drop some drops on your tounge, also you could go to the gp and ask for something to take the edge of while you are learning,
i have foungd that learning to drive was the best thing ever i dont have to rely on other people, being in the south west taxis and buses became expensive,
my brother in law is only 22 and he took several atempts at his test and we think he might be adhd,
good luck