It is a legal requirement that all explosive stores are registered, and most County Authorities delegate this to the County Trading Standards Office or to the Local Fire Brigade.

In Worcestershire, you will need to contact Trading  Standards at:-

Worcester Trading Standards
28/30 Foregate Street
Worcester
WR1 1DS

In Warwickshire, you will need to contact Trading  Standards at:-

Warwickshire County Council
Trading Standards Service
Safety & Fair Trading Division
Warwick
Old Budbrook Rd
Warwick
CV35 7DP
Phone 01926 414021

Ask them for an application form to register your premises as a registered explosives store.

Fill in the form and give as much info as possible. The type of store you are registering is "Mode B". This will allow you to store up to 7 Kg's of propellant and

You will be required to state what is being stored, and this will be:-
Mixed Explosives
Rocket Motors UN0349 and UN0351
Black Powder UN0027 and UN 0028
(Black Powder is required for ejection charges, and this should also be listed)

There is an annual fee to be paid, in Worcestershire it is £13 but this varies slightly around the country

The certificate is valid for one year

Some authorities will only issue a certificate after inspecting the premises, and this visit is often arranged with the visit from the Police Explosives Liaison Officer

Please check with your insurance company that they will still cover you. Most will with no additional premiums, since the Mode B classification also indicates that it is safe.