2/1 London FA appear to have remained with 56th (1st London) Division from Aug 1915 to May 1919, according to the NA catalogue entry for their War Diary, WO 95/2944.
1/1 London FA, according to the Long Long Trail, left 56 Division for Salonika in June 1916 and on arrival, was redesignated 30th Stationary Hospital.
His service number is a post-1917 six figure number, but I can't differentiate which line by it.
Phil