Aston Sandford, Nr. Haddenham
Thanks to forum member Tinker, the entrace to Lower Moat Manor has been found at a small hamlet called Aston Sandford, near Haddenham.
Thanks to Carl Jones who identified that the road leading up to Aston Sandford was the junction in the episode.
The final scene where you see Rayburn as the tramp walking in the fog you can see the church spire in the background. Thanks to Jo (Tinker on the forum) for telling me about this location.