Lovely find. As you say most disconcerting as I can't seem to get a reference point even for the familiar canal junction, but I wonder if the house to the left was this one that was subsequently enlarged? https://maps.google.co.uk/maps?q=52...z-pXmVbLiAQc7rcwdHCzBA&cbp=12,71.09,,0,-12.78
.... Is that Holloway Head windmill again middle distance to left of the chimney. Maybe you can run a sightline on that Aidan. I think that the distant tower is too far west though and again the draughtsmanship is very fine....