without belittling your son, could it be that he is a little too sensitive and you may need to teach him how to ignore personal jibes and rude words, rather than call in the authorities? Have you followed the official complaints procedure of the school? usually teacher, head teacher, governors, then LEA. Threatening LEA for verbal cat calling and name calling seems to be a sledgehammer to crack a nut. Maybe you are being a little over sensitive yourself?
Not minimising verbal bullying, but this is something everyone has to learn to deal with - there will always be people who resort to name calling and swearing, and its something we all have to learn to ignore. If you call in the big guns for a child calling your son a cunt, you are overreacting, in my opinion. Children do swear, the trick is learning when it is appropriate. Leave it to the head teacher to deal with.
The fact that the child's mum is a governor is neither here nor there. They would be asked to leave the room at the point this issue was discussed in a governors meeting (if indeed it even got to governors). Usually this would be dealt with by the chair and two other governors - usually a community and a LEA governor, or a foundation governor in the case of a faith school, unlikely to involve a parent governor. If you get no joy from the official paths, then by all means go to the LEA. But in all honestly, I very much doubt they will take any action for a young child calling yours a gay or a cunt. Or even for a daily ragging about anything.
Kids do poke fun of eachother, its what kids do. I would guarantee your son has said something horrible to someone at some point in his school career. You would be better served boosting your childs self esteem and teaching him how to cope with sneers and nastiness which will undoubtedly continue throughout his school career because kids are horrible to eachother.
Ultimately the bully wants a big reaction from his target. If he gets nothing, he will move on to someone else. He will soon be a very lonely lad.