I believe that generally the only stones that have been moved are the ones that are missing (f not buried) of course there are exceptions but most stones look like they were knocked over or fell over where they stand. Most stones you can see whether they fell toward or away from the circle.
I think that Arbor Low gives a pretty good idea of what a henge looks like along with Avebury, and I at least am happy to believe that the stones lie where they fell if only judged by the fact of the shear effort it would take to move them around - after all if we assume it was The Romans who would have knocked down the circles- judging by the vindolanda tablets - I would say that most of the soldiers couldn't be arsed to do a thorough job of circle destruction. The alternative is that they fell over and who's gonna pick em back up when they finally fell..
Alternatively medival christian freaks could have torn some down with there ever eternal hunt for witches and magic practitioners but again I think too much effort to move the stones around and most of the churchies would be too freaked out by the whole senario that they wouldn't stick around too long anywayz
Its the early archeologists you have to watch out for, with their attempts of Grail hunting and the likes, and early site restoration
But tis just a guess.. who knows?
-broen-
]:-}
