Tabbitha,
By rights, if he was from the Manchester area, he would probably have been with East Lancs Field Ambulance.
I had a quick look last night through the John and Jack Morris RAMC medal index cards. Unless there is a 1917 six digit service number on the MIC, it is virtually impossible to pick anyone out.
I did find one possible, but he was with West Lancs FA post-1917:
Jack Morris, Private 1427 and 341106 RAMC.
Phil