Driving instructors

Hello.

I'm trying to find driving instructors in the Hertfordshire/ Cambridge / Essex borders who have experience of teaching pupils with ASD and I'm struggling. My 18 year old son was learning with an instructor who was aware of his condition and who seemed keen to teach him, but after a year the instructor asked to stop as he didn't feel my son was making progress.

I've contacted Julia Malkin but no ADIs from her scheme close to us it seems.

Please can anybody give me some specific names of instructors  or hints where else I might look?

Thank you in anticipation 

Beeman