The burden of proof moves decidely away from the third way parties to the glaciation party. The third way parties now have a viable theory for how every bit of bluestone arrived. The glaciation party has to explain how glaciers brought bluestones from Snowdonia, the Llyn Peninsula and Anglesey but NOT vast quantities of granite as well.
The "third option" does not seem to me to be a viable theory at all -- just another piece of special pleading, designed to explain away something that is increasingly difficult to explain, namely highly varied lithologies and widely separated source areas for the rocks and fragments. Do you actually want scores of bluestone quarries all over the place? Come off it..... so why aren't there any of these quarries to the north, east and south of Stonehenge?
And I disagree with you about glacial transport. We still don't know whether there are any rocks from Snowdonia, Anglesey and Llyn on Salisbury Plain -- some of the fragments MIGHT come from those areas. And glaciers do not pick up great loads of rock from every piece of landscape they pass across. Can I respectfully suggest you do a bit of homework on this?
