There are ALLOT of legal issues behind that. I have to assume to people who buy those chemical build fireworks in a legal manner (If you don't, please don't use the forum to advertise this fact!!!), but I suspect that HSE and other regulators will ask the question at some point. When that happens, I doubt if the society will want to be a part of the scene. From my personal prospective, the first step is to get exemptions for the hobbyist community, and when you get a legal status, worry about the suppliers.
(Please don't start discussion about the law following this post. I post it here to explain the problems about allowing trade on the forum. Legal issues should be discussed in the law thread.)
Just wondering - does anyone have a rough idea how many licensed explosive factories there are in the UK (that manufacture pyrotechnic items?) I can't imagine there are very many at all.