I think it is necessary to keep the milking scene in sequence, as things happened at White Place Farm to show how the second Lord Astor progressed with building his model and most modern farm, especially in the 1920's and 30's.
Building is 19 and 20 on the farm map, were the first cowsheds to be converted to milking machine use in the early 1920's. Building 21 was a purpose-built building shortly afterwards, but it was taller and more airer, with plenty of light, plus it had a foot bath for the cattle to walk through both entering and leaving the cowshed. The older buildings 19 and 20 did not have this facility at all. Lighting for these buildings could have been one of the DeLaval vacuum pumps, but instead it was powered from a generator located in the pumphouse, (building 26 on your farm map.) This remained in use until mains power arrived in 1943.
This early vacuum unit is a compact view of the system and shows the option of having an electric generator run off the vacuum pump petrol or diesel motor.
This diagram is to show the plan layout of both buildings 19 and 20, building 21 was much larger with a similar layout. As for the stalls and milking machine. The blue line is the vacuum piping which was installed in about 6 feet and the crossover the doorway was about 8 feet.
This is an example of an early bucket unit in the 1920's. Note the four teat cups affixed to what was known as the claw, and the heart of the system or pulsator mounted on top of the lid of the bucket. After every milking, the units were taken apart and cleaned and reassembled in the dairy.
As the cattle spent quite a time in the cowshed. It was necessary that each cow should have their own drinking fountain or bowl. Figure "A" was the nose operated tap, that when depressed, water would flow into the bowl from the water pipe "B."