Two more Sleek Stone Erratics

I'm rather intrigued by the top two photos here -- these are both erratic pebbles from near Sleek Stone.  I'm interested by the dark matrix and irregular rather jagged inclusions which make it look like an agglomerate of some sort... or is it an ignimbrite?  The inclusions, when eroded on the surface of the stone, have an almost silky feel to them.  And the colour is unusual too -- with subtle variations on the rosy pink / cream / foxy brown ens of the scale -- very different from the blues, greens and greys of most of the igneous rocks found on local beaches.

These pebbles remind me of the stones found at Aber Mawr and on Newport Estuary in the past:
http://brian-mountainman.blogspot.co.uk/2014/10/another-mystery-erratic-from-abermawr.html

For comparison, I've added the bottom photo of the rough conglomerate boulder found by Chris on Flat Holm in October.  The colouring is similar, but the texture and the nature of the inclusions are quite different.

Any ideas, anybody?