>No way are those stones acting as the main support.<
You're quite right Nigel, and if you take another look at http://www.liminae.co.uk/pages/england_wiltshire_pewsey_church.htm you'll see how the bottom-most stone of the corner buttress has been cut so that it appears to be holding or growing from the sarsen. I think there's little doubt that this is a symbolic statement by the Church rather than a structural necessity or the whim of an eccentric Victorian clergyman (especially as there's evidence of sarsens being placed in a similar way at other churches in the area). And not only within the Avebury area but further afield as well (for example Peter's observation that the practice also appears at Broomfield in Essex, where, "...a large pudding stone... is partly inside the church and partly outside, SUSPENDED about a foot from the ground and protruding about two feet from the exterior wall."
The pivotal question is, "Is this deliberate placing of stones in the foundations of churches an attempt by the Church to demonstrate <i>dominance</i> over an earlier belief system or an attempt by the Church to incorporate that earlier belief system into Christianity? I'd opt for the latter and, if correct, it's perhaps safe to assume a far greater continuity of pre-Christian traditions at these places than we may have hitherto imagined.
