The Chossy range of saddle bags was manufactured by the C.T. Osbourne Co. Ltd.
As of May 1950, their range comprised 11 different bags and panniers. This listing, in the 19 May 1950 issue of The Motor Cycle and Cycle Trader doesn't specify the materials they were made of however.
In addition to Chossy, other British manufacturers of saddle bags, pannier bags and sundries were:
Attennborough Brothers Ltd. Baycliff Ltd. J.B. Brooks H.W. Carradice Gill & Smith Ltd. Holdsworthy Karrimore Weathertite Products Midland Gear Case Arthur S. Waltho
Peter Kohler
Washington DC USA