Following up on the dairy theme there's a small snippet in the Livestock Journal of 1922 that would suggest that the milk (and good quality stuff at that) was still flowing freely at that particular time
HOLLY, W. & SONS, BERRYLANDS, SURBITON. Registered herd, Pedigree heavy milkers. Societies milk records, tuberculin tested. Stock bull (Stagenhoe Governor) has won several first prizes, Champion Cup at Reading, also Silver Medal Dairy Show 1920; also numerous prize-winners, including first for best heifer, second in Milking Trials and Silver Medal at London...
Even up to 1939 the Holly family seem to still have been a force in the club as in that year records note that the "... prizes will be presented by Mrs W Holly (president)." Sadly she died later that year in her 70s and I would imagine that that and the post war building boom might well have been the catalyst for the final break up and sale of the remaining land and whatever remained of the dairy herd itself.
One last little mystery caught my attention, and that was the fairly plain mosaic in the shop front to the left of the arch. I imagine at some point that this could well have been the dairy shop but sad to say I can't be sure because whatever name in the middle was originally, it's been very thoroughly erased by later owners!