The sale and use of fireworks in England and Wales are governed primarily by the Fireworks Regulations 2004 made under the Fireworks Act 2003. The law is basically the same in Scotland, where the 2004 Regulations also apply alongside the Fireworks (Scotland) Regulations 2004. The position is different in Northern Ireland, where a valid licence is needed to buy, possess and use fireworks (except indoor fireworks and sparklers).
More detail is given in a Commons Library Briefing:
Regulation of fireworks, Commons Library Briefing Paper CBP 5704, 6 November 2018.
A Westminster Hall debate on E-petition 231147 relating to the sale of fireworks to the public is scheduled for the previous day, Monday 26 November 2018. The Member leading this debate is Helen Jones MP. The Commons Debate Pack published for this earlier debate, may also be of interest in respect of this debate on 27 November:
E-petition 231147 relating to the sale of fireworks to the public, Commons Library debate pack CDP-2018-0259, 22 November 2018