The are called Grey London Stoneware. We didn't chose them because of the name! They are a slightly textured pale grey. We though pale would be good not to pick up too much heat from the sun, and we wanted fairly neutral as there is a lot going on already with the stone and wood. There will be a bit of color in the (small) red tiled work surface.
We are planning on rendering/repointing stonework with white lime, a sample of which is on a slate beside the tiles. A bit of the wall has experimentally got grey lime, to the right of the slate. We are planning that it is quite rustic and rendered with some bits of stone showing through.