http://news.bbc.co.uk/2/hi/uk_news/wales/south_west/4123764.stm
Is there any possibility that there is a stone quarry UNDERNEATH Stonehenge?
It would have been possible to remove the dirt and leave the stones exposed in the formation.
I still believe it was physically impossible for humans to drag those monsters 240 miles - without a thousand dray horses on rotating shifts.
Lots of things are possible -- with enough people over a long-enough time frame.
As an alternate possibility, how cold might British winters been at the time? Instead of stone balls, could they have poured water along the path, had it freeze, and had a huge party at the winter solstice, moving the stones a couple of miles every year until they were done?