Currently make flash powder compositions using simple chemicals. My supplier is away and its coming up 2 fireworks day, I told my friends I would show them a simple flash composition but I can't now. Although I now think I could strip a firework and use the black powder contained inside. Would anyone be able to tell me the structure of a firework or any links to diagrams? :)

First of all, fireworks are just chemicals that ignite and create heat, light and sound etc. They don't have to have any particular structure, unless we are talking pyrotechnics. That can get very complicated.
Graphite, Saltpeter(potassium nitrate, which is the oxidizer here) and sulphur that'll make a bang plus that is pretty much old fashioned gun power.

Structure? I think you mean what are the main compnents. You need any oxidizer, fuel & catalizer