I did
brief stats for World War I motorcycles five years ago. I need to revisit that at some point for the machine gun sidecars used by some units. A British Motor Machine Gun Battery had 29 or 30 vehicles:
6 motorcycles with sidecar with Vickers MG
6 motorcycles with sidecar as spares
6 motorcycles with sidecar as ammo carriers
1 motorcycle with sidecar for the CO
8 motorcycles without sidecars for scouts/couriers/extra men
2 or 3 wagons or cars for cargo transport
Once the Western Front had settled into trench warfare, many of the soldiers from these units were moved to the Tank Corps.