Best guess is near Badminton in South Gloucestershire. Deer park, Roman villa and settlement and The Grickstone.
https://historicengland.org.uk/advice/heritage-at-risk/search-register/list-entry/43254
I think you may have it! Someone has just told me "There's only one deer park in that area of South Glos as far as I know, that is at Dyrham."