The Tile factories team suggested it was possible that the adhesive was too thick. This in turn has caused shrinkage. Fault with the tile? Very slim chance. We had 1250 sq.mtrs from that batch delivered and this is the only issue we had with them.
Coupled with what you guys have said about not using any form of corner expansion, you'll also notice on 2 of the pictuers, the cracks follow in an almost straight line from one tile to the next, implying that there is something going on underneath and the tiles are following.
As for the wall in the shower.... still at a loss on that one, and can only assume that what has affected the corners has also affected the remainder of the wall.
Having spoken to the customer, the same adhesive has been used in the dry areas of the room too. Onto plaster but only a couple of cracks were noticed early on. This hasn't got any worse. But the large areas with the cracks is where the homelux wall matting was used and have continued to crack further since they were fitted and the shower has been used.
I have since spoken to the factory again as I'm not going to go running back to the customer and say "its been fitted wrong". It want the factory to actually run their own tests to draw a conclusion rather than just assume whats happened. Of course in their eyes its not a fault with the tile. That'd just be silly