Lottee,
Ady is exactly right. By January 1916, when ‘attestation’ was not drawing in men in the numbers required (basically, ‘attestation’ was a system whereby men who signed up would only be called upon when needed) the Government introduced the Military Service Act. This meant conscription for single men, and extended soon afterwards to include married men as well. So by 1917, the Army was mixture of regular soldiers, conscripts, volunteers and part-time soldiers. As a result, any given unit was made up of men from different parts of the country, and by the end of the war, men from London might be serving in a Scottish unit, Welsh men might be serving in English battalions, and so on. As Ady rightly says, men were sent wherever they were needed.
This may be a silly question, Lottee, but how do you know that this man was actually a member of the Armed Forces? Do you have some sort of documentary evidence, or is this simply an assumption (which is perfectly reasonable, of course).
Regards,
Peter