Apologies for the lengthy thread title.

I'm attempting to construct the military career of Lt Guy Harris who was associated with the RAF's development of airships between 1919 and 1920.

Harris was born on 6 September 1884, location unknown but in 1919 he and his wife were living in Birmingham.
There is some evidence that he was working in the Met Office in London circa 1910-1911, but he did not start his military career until 28 August 1917 when he was commissioned as a Sub-Lieutenant in the RNAS and posted to Howden Airship Station (AS) for meteorological duties.

On promotion to Lieutenant when transferred to the RAF on 15 August 1918 he remained at Howden. On 25 March 1919 he sailed to Canada on the SS Montcalm to demonstrate the feasibility of flying kites to obtain upper air information in anticipation of RAF airship flights across the Atlantic; he continued the experimental work on the return voyage, docking in Glasgow on 1 May.

His next posting was to South Fortune AS where, on 2 July, he was the meteorologist on the R34 as it began its flight to the US. After a three day stop the R34 returned to the UK, landing at Pulham AS on 13 July. Harris was awarded the AFC for his contribution to the successful flight.

I think his military career ended on 13 Jan 1920 as his service record advises his transfer to 'M' List

Could I ask (1) What the 'M' List was and (2) does his name appear in any subsequent Air Force List as, to all intents and purposes, he disappears from the face of the earth.