Neolithic climate change

Continuing on the theme of what might have been optimal environmental conditions for stone-pulling on Salisbury Plain, it's difficult to sort out from the pollen and other records what short-term oscillations were truly climate-related, and which one were related to human activities like forest clearance, increased agricultural activity etc.  However, it does appear that in the Neolithic the climate was cooler than it was in the Mesolithic -- the relatively warm period dated to 8,000 - 5,000 BP is often called the Holocene Climatic Optimum.  The climax vegetation seems to have shifted from a southern type of deciduous forest to one with a more "northerly" aspect, with more conifers.  Was it also drier?  It's difficult to say, from the current evidence.  But later on, during the Bronze Age, there is much evidence (from the Somerset levels and elsewhere) to suggest that it did get significantly colder still, and also wetter, with raised water levels and more boggy conditions. 

So could it be that during the Late Neolithic, with cool and moderately dry conditions, and a relatively well-cleared and open landscape, the Salisbury Plain grasslands (with a well-drained chalk substrate) presented ideal stone-pulling conditions?  And could it also be that before a few centuries had passed, the weather turned nasty again, and that that might have limited the range over which the stone-collectors could operate?  If all the stones had already been gathered up over a radius of maybe 30 km, maybe the "cost" expressed in terms of manpower and human effort simply became too high for the Stonehenge project to continue?  And there does seem to be evidence that during the Bronze Age society was changing anyway, with a greatly reduced interest in doing spectacular things with heavy stones.  These are intriguing possibilities......