LOL, that's a strange dog you've got there.
Horse are funny with their odd phobias - we had a road near us and for some reason every horse we owned hated a small stretch of it even though it looked totally the same as all the rest of the road.
The vet said the best start would be obedience classes and from there the teacher will be able to suss out any issues that need more intensive work. He didn't recommend one in particular because he thinks the best class is the one that fits your budget and schedule.
There is a dog club not far away with a Wednesday morning class starting in October so I think we'll roll with them. The RSPCA is close by too but their class is Saturday and although 1 course is cheaper you have to pay per course where the other club is more expensive to join but once you join you can go to as many course as you want in the year.

*sigh* Now I have a dog to run around to extra-curricular activities too.