I haven't seen Dave Fields' article but is he saying that the stones drifted naturally over a period of what... 2000-3000 years to their present location? That seems a hellava long way for a sarcen walk-about over a reatively short period of time.
Could the stones not have been dragged to their present location by the usual "Off my land" mentalilty of local landowners - much as were the Sanctuary stones?