Many of the answers can be found here:

http://www.britarch.ac.uk/ba/ba107/feat2.shtml

Whether it is a puddingstone:

http://en.wikipedia.org/wiki/Puddingstone_(rock)

or another type of conglomerate, I could not find with a web research..

I always believed, to be a puddingstone, you needed large, rounded pebbles in a much finer grained matrix with quite a lot of matrix-pebbles. A conglomerate can have very little inbetween the pebbles (although a puddingstone is still a conglomerate!).

It does appear that the stone is local in origin as it is implied there is a natural outcrop just below the surface...