Stuving (almost) smashes it!
To put anyone else out of their misery, the remaining "non-equestrian" one I intended to refer to was Hinton Manor. There are two country houses of this name in GWR▸ territory (one near Faringdon, another near Marlborough) ..and yet another near Waterlooville in Hampshire. I cannot find which of the first two the GWR intended to honour, but as the last was in Southern territory I assume it was not that one.
I was thinking of the Hinton Manor in Hinton Parva, which is near Lambourn and thus near neither Faringdon nor Marlborough. The relevant data I found was:
Hinton Manor, formerly the home of racehorse owner Michael Talbot-Ponsonby and his family ... Michael Talbot Ponsonby was a racehorse owner and a keen huntsman, hunting with both the Warwickshire and the Heythrop until 1995.
Parishes are notoriously numerous, with the same name cropping up many times over in different places. Manors are worse, with several per parish in some parts of the country.