I don't think Castle Combe is National Trust but, like Lacock, it got itself sorted out by banning parking in the High Street and building a large tarmac carpark outside the village. In fact, the carpark is so outside that it's a good fifteen minutes walk, with no pavements, downhill to the village itself! If Castle Coomb can do it so can Avebury. But let's stop kidding ourselves, there's plenty of land around Avebury which could provided the necessary facilities and overnight stays if the will were there but the fact is that the will isn't there - at least not from local residents (though they seem to have found plenty of land for their social club, its carpark and the huge playing field at the back of the club. There's not even a pedestrian crossing from the Red Lion to the circle - perhaps the residents don't like to see white lines on their roads either ;-)