Firstly, a bit of background gathered from newspapers. Norah Edwardes, daughter of trainer George Edwardes, married Pat Hartigan, trainer. J.F. Davidson took charge at Ogbourne temporarily after the death of Pat Hartigan. About a year after Pat died Norah married his brother Martin Hartigan and the couple trained racehorses at Ogbourne. Pat's will in newspaper gave his address as Bonita, Ogbourne. George Edwardes' brother, Major Edwardes, trained at Bonita Stables in Ogbourne. Also, a newspaper report said at one time the stately residence "Bonita" was the home of Mr. George Edwardes.
I was drawn to these photos in the newspapers of Ogbourne Stables and Bonita from 1908 (Bottom Yard) and 1908 (described as Bonita) when George Edwardes' brother, Major Edwardes was trainer there. Could the house in the photos be the back of the one we are looking for? If you look at "our" photo there is a building to the left, a little lower down, that could be a stable block.
Here's a link to recent photos of the stables, the house is now gone, just trees. Scroll down to the photo of bottom yard.
https://www.windsorclive.co.uk/documents/79_bonita_particulars.pdf