The north yorkshire moors guide stone is almost certainly somewhere near the (western side of) hole of horcum / skelton tower / levisham bottoms area, probably on the roman road that runs through there between pickering and whitby. I have a memory of seeing it while on what is now the 'hole of horcum circular walk' about 40 years ago.
Fascinating. I was hoping to see the "zero mile" marker in Alfreton and it was present. The fingerpost in Brownhills (in the West Midlands) is worth knowing as well: