I do like those satellite photos. I've spent hours staring at the ones of Northumberland.

Looks like the end of the road in terms of websearching then. Time to go delving into old papery records? Hopefully someone will have written something about it, somwhere, at some point.

If you can find out who the county archaeologist is, they'd be the logical place to start, they'd have the county sites and monuments register which should record non-scheduled stuff, at least stuff that's still got remains visible above ground.