Haven't stayed here myself but have heard that it's good (and maybe very good if you're looking for family accommodation) - http://www.bnbselect.com/bnb/38448

For the single or double visitor to Avebury, Mr and Mrs Dixon's B&B at Avebury Trusloe (one of the four semi-detached houses at the top of the hill between Avebury and the Beckhampton roundabout) is pretty good (excellent breakfast in Mrs Dixon's kitchen and only a short walk to Avebury and The Waggon and Horses at Beckhampton). The front bedroom has a view of Silbury. If you take the lanes and paths to Avebury, Silbury or the Waggon and Horses you'll miss the main road - except where you actually have to cross it.