It isn't certain that the 3 Reserve Depot was at Woolwich in 1912, the LLT refers to the war years,although it was the home of ASC records to which he was told to report in 1912. So all we can say is that some time between then and August 1914 he found himself in Dublin where he was mobilized in August 14.
His medal card records only one unit, Base Horse Transport Depot, and must refer to the beginning of his active war service. On his conduct sheet, above the details of his court martial, one can make out the very faint words "AF (Army Form) B122 (the conduct sheet) was received with this man on posting (illegible) Base Horse Tpt (transport) Depot Havre (Le Havre)". No 10 Company was there with 1 Base Depot from Aug 14 so it is highly likely that, although there is no date on the extant conduct sheet, he went to Le Havre from Dublin arriving on 23 August 1914 (date on his medal card). There is a diary for 10 Company for the beginning of the war
http://discovery.nationalarchives.gov.uk/details/r/602a8c6240b3445e9fd08f9b4200cf04The faint entry implies, although one can't be certain as obviously much of his record is missing, that he went from No 10 Company to 426 Company, there is no record of when this happened . All that is known is that he was with the 1st Indian Cavalry Division at the time of his court martial in 1916.
Another invisible area is where was he after 1st Indian Cavalry Divsion was broken up in March 1918. The later diary for 426 Company
http://discovery.nationalarchives.gov.uk/details/r/C7351568appears to show that the month of January 1918 was spent in dispersing men, horses and equipment in all directions. There are no clues as to where any individuals may have gone and there is no further diary. He didn't return from overseas until May 1919 so there is a large gap there with no indication on his record at all. Frustrating I know but par for the course, particularly when his record is almost devoid of useful dates and units! My feeling is we have squeezed as much as is possible out of the record.
maxD