>The clearer things are, the better for everyone.
In defence of Stonelifter's assertions that there are prehistoric remains on the moors west of the South Tyne Valley, the Beckensall archive has an example of a pretty convincing marked stone. Iv'e posted the link to tma for the sake of context. http://www.themodernantiquarian.com/site/8094
It's worth pointing out that it where such motifs are found, there are usually burial monuments nearby. Not a vast amount of help, as some of the features have described as possibly medieval, and hence this stone may have shifted a way since it was carved, but it still indicates there is a decent likelihood of there being prehistoric stuff around there at some point.
I think the main difficulty you're going to have SL, is that all that mining will have obliterated much of what was there. Still, there might be another nice prehistoric gold basket earring that some riever dropped hundreds of years ago after ripping into a cairn on his way to trash one of those medieval mining sites.