So your Grandad can't be in the photo.
His MIC has him as an Acting Sgt.
If he was in the photo he would have stripes & you say that there are none also his cap badge isn't Worc. Regt.
So it looks like Uncle George & A.N. Other of the MGC.
I don't have access any more to old newspapers.
Looking at the service numbers I would say your George would have to one of these:
George Saunders
Duke of Cambridge's Own (Middlesex) Regiment, Machine Gun Corps 51043,149479
George A Saunders
Machine Gun Corps 145080
George Saunders
King's Own Royal Lancaster Regiment, Machine Gun Corps 34892,176761