'Standard' fireworks licenses only allow suppliers to sell fireworks for a period of three weeks, a few days before the New Year, Diwali and Chinese New Year. There are many websites that provide the best selection of fireworks.
If we deal with what must be purchased first, the most important thing to look for is that fireworks comply with British Standard BS7114. This number must be printed on the box or fireworks, and indicates that the product meets strict safety standards.
If you don't see this number, just leave it. These fireworks should not be offered for sale, but unfortunately, the non-compliance fireworks still slip through the net.
Fireworks are divided into four categories, only two of which really concern us here. Category one is for things like indoor fireworks, and category four is for professional displays, so most of what you see in stores is in categories two and three.
The main principle for category two fireworks is that the fuse must turn on between three and 13 seconds, and it must be seen from at least five meters away. There are also criteria for areas of falling debris, but these are the main criteria that determine.
You tend to get category two fireworks in smaller display boxes, sold through major suppliers such as newsagents and supermarkets. The more spectacular three item categories are usually sold as individual items, and can usually be found in more specialized outlets.