What type of tile trim would be required for the vertical corner edge shown in red below? Would it be this type? http://www.toppstiles.co.uk/tprod4367/internal-cove-white-6mm.html
As it says in the description that one is for an internal corner. I would have thought that a conventional external corner bead would suffice however you might have to make angle cuts on the edges of one set of the tiles to meet the bead properly. It will depend on the angle of the return and possibly the choice of tile. This is where heavily chamfered metro tiles become more difficult to make cut edges look good.