Hi Shirley
Having two 'corps' rather than much smaller infantry battalions will make this a mammoth task. The Labour Corps was not created until the start of 1917. So he went to the Balkans with the ASC - Royal was not added until late in 1918. There were 325,000 in the ASC at its peak. Normally their numbers have a prefix that gives a start as to which branch he was in.
http://www.longlongtrail.co.uk/army/regiments-and-corps/the-army-service-corps-in-the-first-world-war/If you check out 1914-1918.net you may find which divisions were in the Balkan theatre, and which divisional ASC were present. They all did similar work. But the lack of a prefix may hinder further progress.
You could ask on the Great War Forum for an expert in the respective numbers to tell you when they were issued.
Mid 40s was the upper age limit. Also, in his case, the fact he was earmarked for the Class Z Reserve at the end of the war, shows he was still fit. They were created in case fighting started again. Men were sent home but had to be ready to return if fight recommenced.
As he was old enough to vote you should check out the electoral roll for his home address (if you have it). It may give more information.
Ken