I really hope your son gets the help he needs. It's so hard when you're fighting for really fairly simple things, which will make such a difference to his life.
I understand that it can seem like an unwarranted expense to put a child with SEN in a private school which is more geared to their needs, but after paying out for a TA, specialist equipment etc, I don't really think it is any more expensive. LEA's need to remember that, while they have 100's of tries each year to get education right for children, and individual child has only one chance.