If you google, there is a programme from 1930 of the Mincing Lane Dramatic Club for sale on ebay. (it lists the orchestra members)
I can see newspaper articles, probably the same as you have already. One from the Daily Telegraph (Tuesday, Feb. 10, 1925) says the members were all from the London tea and rubber markets, and that this was the fourth annual production, so began in 1922.
Another article from the Daily Telegraph mentions the orchestra, under the direction of Mr F. D. GOOCH.
(Tuesday, Jan. 29, 1929)