Zodak... NAR is the National Association of Rocketry, Tripoli is another Rocket Association, they are the regulatory bodies (in the US) As it stand in the US the general public can buy motors up to G class motors, to launch H or higher you have to be certified (ie you have to prove that your rockets wont be a danger and stay intact) Level one Cert allows you to launch up to I, then you have to get Level two, which involves bigger motors and a written test covering rules and regulations, that qualifies you to launch up to L motors, then you go for Level 3 which technically allows you to launch any size motor you can afford... I dont know the rules in britain but http://www.ukra.org.uk/ is your organization