When we used to go to the top of One Tree Hill there were railings to the back making it safe as behind was a very steep drop much like a cliff edge, looking down there could be seen near the rear of Honour Oak Station allotments and nearby a series of wooden huts, these on closer inspection were used to make Fireworks, the place was very near facing 103 Honour Oak Park.
I cant remember the name of the Manufacturers but they were very popular in the local Shops.
I have found a picture of some sheds and huts where Fireworks were made but they are not the huts in question.