I was reading something recently (can't remember what, Hengeworld or Aubrey Burl's Stone Circles Of Britian, Ireland and Brittanny probably), that stated that near many 'ritual landscapes' such as Avebury that there is evidence for other man made hills (the book gave a long list of examples, but blow me if i can remember any apart from Silbury).
Anyway, i recently visited Stanton Drew, and noticed on the map a hillfort as short distance to the North called Maes Knoll, which dominates the skyline to the North of the Circle (which is roughly oriented to the NE, well it has a small 'avenue' in this direction, but outlier stone called Haughtvilles Quoit 400m directly north).
Well , to get to the point, Maes Knoll contains a large 'hillock' called Maes Knoll Tump, which is reported to be 60 meters across, and about 15 meters high, and is attributed to the Saxons, but because there has been no excavation of the site, the date is unknown. Maes Knoll also happens to be the Western terminus of a much later linear earthwork called Wandesdyke. Is it possible that the Meas Knoll Tump is a smaller version of Silbury, or am i sounding a bit like Bert?...I'll get me coat.