Small bore English guns, regardless of manufacturer, have always been a scarce commodity. Eley [IMI] Reported cartridge [Shell] sales in 1980 as follows:
12.G-87% 16.G- 3.2% 20.G -3.2% 28.G-0.5% .410-6.0%
These cartridge sales are I believe a good indication as to the mix of guns produced by English makers.

Roy Hebbes