Interesting subject, topical now Fireworks are again on sale in many UK High Street shops. 5th November draws closer and already people are letting them off at night.
Hounslows' Lampton Park firework display is probably the most relevant in this, usually Sat 6th November - they have a mass fireworks & bonfire show right on finals for LHR 27R.
Remember watching the show (+arrivals) a few years ago during the show, fireworks appeared VERY VERY close to BA 767s and A320s on finals for 27 right.
Diwali festivites at a similar time around the Hounslow & Southall & Slough areas aslo see lots of high performance light shows & firecrackers going off around LHR.