The Firearms Act 1968 (as amended) prohibits the possession of expanding ammunition.
However, Section 5A(4) allows a condition to be added to a firearm certificate for possession of expanding ammunition for:
the lawful shooting of deer
the shooting of vermin or, in the case of carrying on activities in connection with the management of any estate, other wildlife
the humane killing of animals
the shooting of animals for the protection of other animals or humans