Sorry Simon, but whilst we're in the area of Arkengarthdale can I confuse you with more alien names and places and issues just over the road from the above? Possibly more of a headache than moving photos about.

Cut'n'paste from an old thread:

"If you click the mines within 10km button for a few of the levels on and around Marrick Moor in Swaledale the results show mines in the wrong areas.
At a glance Hurst and the Fremington Edge Chert quarries link to mines around the Cleveland Hills and Fell End and Shaw link to the mines around Richmond rather than Marrick and Arkengarthdale
The NGRs appear about right so I'm not sure what the problem is. Strangely none of the links are reversed and none of the Marrick levels link to each other."

Yup.
On the 10km links, Hurst links to Snotterdale which will be about 30 or so miles away but not Fell End Low which is a mile or so away.

http://www.aditnow.co.uk/mines/Hurst-Lead-Mine/ 
http://www.aditnow.co.uk/album/Snotterdale-Jet-Mine-User-Album/?uid=988 

I think a comment was previously made re that it might be due to it being towards the edge of the sheet, the relevant ones in this case would be NZ, NY and possibly SE.