I have quoted this from the above link......from....Controls on possession of component parts of ammunition.
"Only the main components of ammunition are already controlled (propellants and primers). The possession of propellants is controlled under the Explosives Regulations 2014 which require that, with certain exceptions, anyone wanting to acquire or keep explosives must hold an explosives certificate issued by the police."
As I understand it, I only require an explosives licence to store and transport my Black powder, and not for propellants, or have I misunderstood.