Ah great minds think alike eh?!
It seems Silk Hill is on here - it's
http://www.themodernantiquarian.com/site/4020
I had a look on magic and there are so many barrows - 12 are listed, but you'd imagine some have been lost.

It's good to be able to read the book online, but the navigation on the website's a bit dodgy I thought. I thought it was interesting how he likes to be all Scientific and Rational, and then he comes out with some airy fairy stuff about being closer to the gods. But then you can't go to these elevated places and not feel like that! I was reading a bit about him going to Adam's Grave and he took great delight in spotting all the places in the landscape he recognised. The human condition eh.