The Cromlech Challenge

On a number of occasions in the past I have referred to Steve Burrow's book called "The Tomb Builders".  Here is one post, from 2011:

http://brian-mountainman.blogspot.co.uk/2011/01/inside-neolithic-mind.html

Essentially, Steve's research leads him to believe that all of the cromlechs in Wales were built from stones simply collected from the vicinity - from handy broken rock outcrops, from bedrock stone litter in the landscape, or from glacial erratics.  I know the Pembrokeshire megalithic monuments pretty well, and from my limited experience, I think Steve has got it right.  I would extend the "local stone use" thesis to Bronze Age standing stones as well.

So here is a challenge.  Does anybody have any evidence that can be used to undermine this assertion?   If so, let's hear about it..........