The keys to the past grid ref puts those here:
http://www.flashearth.com/?lat=55.665924&lon=-1.933344&z=16.8&r=0&src=msl
(edit:)
which looks crud on flash earth, but the google earth shows these lovely things:
http://www.themodernantiquarian.com/post/64637/northumberland.html?stream=date
which are in the same spot. I reckon you got it nailed Baza.