Shooting rights are a bit of a quirky British law that often surprises people.
Basically, the right to hunt, fish or shoot can be sold separately to the actual land. So I could own the shooting rights on a piece of land that you have the deeds to and still be able to enter it and shoot across or on it without you being able to do anything about it.
Normally, land is sold with shooting, fishing or hunting rights included so the owner holds them and can give permission.
You need to find out if the landowner holds the shooting rights, if he does then ask him for permission. If he do