Never found it since!!...wound me up writing that. So today I made sure I chuffin' well found it again.
Easy to miss and not a deal there when you find it, it has to be said. The kerb/rubble bank although overgrown is very wide with some good coarses of stones visible in the heather.
The site is marked as being in a 'Danger Area' on the O.S maps (rifle range), so keep your head down if there's red flags about.
I was once taken up here years ago. There wasn't much to see, a low rubble bank and stones that may or may not have had something to do with the circle, and it was very overgrown.
Never found it since......