Dear Rhiannon,
I'm new to this, so apologies all round if this message comes up - as I suspect it will - in quite the wrong place. I'm in fact chasing a ref you gave in another posting on Ordnance Survey benchmarks at Avebury - I have found a photograph from the early 1940s of a stone at Avebury with a benchmark apparently painted onto it. Any chance you could let me know the ref for the Wiltshire Archaeological Magazine bit you quoted?
All best wishes
Kitty Hauser