Not sure about that, but taking portal tombs, and their placement in the welsh landscape, i.e. under a rocky escarpment or crag, than possibly these places were firstly mesolithic. There is a couple of very low portal tombs on the beach in sw.wales, which surely must relate back to the sea and mesolithic occupation - sea food, etc, but are these sw. sea facing tombs looking towards, the sea or Ireland - land from which these people came from. Mendips on the other hand shows a continuity back through neolithic and mesolithic, again a place of caves and rocks, but has there been a continuous or a discontinuous thread??