Being headshy is actually the norm for snakes.
After all, that's where a predator will aim for to quickly disable and kill a snake. Some snakes will slowly overcome being headshy, if you are extremely patient and work very hard at it.
Plenty will never outgrow it, so just try and accept that fact. It doesn't have any bearing on your relationship with your animal.
To begin trying to overcome it, only approach the snakes head from the back. Move very slowly, and don't allow your hand to come in front of the snakes eyes, that will startle it and you will undo your work. Softly touch the back of the neck and base of the skull, if the snake will allow it.
Move very, very slowly. Take your time and only touch it once each time you handle him.
Gale