Hello Rivington Pike, welcome aboard! This is the first time I've spoken to a hill... I think...
That stone definitely looks interesting - I reckon there's a lot of prehistoric stuff just waiting to be discovered all around Winter Hill, especially around Anglezark, under all that peat. As I've said before in my fieldnotes on TMA, everything seems to point towards Winter Hill and/or Rivington Pike. Pikestones in particular - even the name points to it! Have you seen this:
http://www.themodernantiquarian.com/browse.php?site_id=3467
I've tried visiting a couple of times now, but to no avail - one time I was turned away and the other the place was locked up. It was found in Anglezark reservoir - and begs the question, what else lies beneath the reservoir's surface?