Morning Lynn,
The cap badge, does as you say, look like that of the Army Service Corps however a better high res' scan of the badge may confirm that. The wheel on his upper arm is a trade badge and indicates that he was a wheeler and carpenter.
The wearing of the bandolier across his chest would signify that he was mounted and as he has a crop in his hand I would suggest that he may have been a driver within the corps. Having looked on the MIC's held at Kew there appears to be 23 James Morrison's who served with the A.S.C. so unless he had a middle name you may have difficulty in obtaining the correct medal card for him.
OR