Gerryh,
I have always believed that the "Call to Arms" in 1914 prompted men of all classes, professions and trades to immediately respond to that call, a belief reinforced by an examination of the Manchester City Battalions Book of Honour. I cite just one name as an example - W.M.Johnson - Chairman & Managing Director of R.Johnson,Clapham & Morris Ltd., Manchester, 16th Mcrs. Kia 2.7.16. The Manchester Education Committee lists 3 pages of names of teachers serving with the Colours, including women teachers serving in Red Cross Hospitals. This belief is strengthened by the fact that my father, my uncle and my wife's relatives enlisted within the first few days of the commencement of hostilities. You possibly would place these men as "middle class". I do not think it was "a knee-jerk reaction", in the same way, that early in 1942 and under age, I felt compelled to volunteer for pilot training. This was no knee-jerk decision.
As regards the enlistment of teachers and "intellectuals" into the Army, I would call your attention to the 20th (University & Public Schools) battalion Royal Fusiliers which enlisted men in Manchester and whose title describes the source of its recruitment. Robert Graves describes in "Goodbye to All That", that the men of this battalion were "chocolate soldiers" - my relative being one such soldier, but nevertheless he managed to win a Military Medal before being wounded and subsequently dying in the High Wood battle.
As regards 'conchies" and the 1916 Military Service Act, the situation encompasses all sorts of reasons for delaying enlistment, not least in the matter of Reserve Occupations e.g. Army Boot production in Northampton.
In closing, I trust you are well, and I sense that another of your books is on the way? Regards. PhilipG.