This is getting more and more exciting as a theory.

The idea that the bluestones were a pre-existing circle has been mooted before - and makes more sense than the reverse IMO but I seem to recall a geologist saying they all came from widely spread strata - is that correct?

One interesting effect of the theory is that it throws the glaciation one out of the window of course.

Another is that the sarsens are of secondary importance maybe, and are just there for show! Actually Goff, as a well groupie maybe you'll empathise with that - they're unlovely, a bit crass and maybe just there to provide an impressive setting to the really important bit - which is exactly what the Victorians did to a lot of sacred wells...