I'm not really sure if they had pre-formed lines but they are definitely Villeroy and Boch Bernina Creme 3.3 x 7.5cm Mosaic. It looks from the web site as if they come in a large square like your image above but I thought they pulled apart into individual mosaic tiles.
Arghhhh .... these are Mosaics on a mesh...just checked with Waxmans who sell them.
I would be tempted to try and remove the grout first and regrout before ripping them off. A multi-tool should take this gout out quite easily, worth a try and possibly money saving.
Thanks Tom, I really appreciate your checking this out for me. I think I'm going to find a local tiler and get it done properly, not sure I trust myself with the multi tool, I'll end up cutting through the tiles lol!
Final question. I know the cracked grout is going to let water through, but would those cracks allow enough through to cause this problem? There's no direct water jet onto that wall, it's only going to get sprayed (although we do admittedly have a 4 bar pump pushing the water upstairs). I'd have thought that any water would drop vertically but is it possible there could be a leak from behind the hand held shower outlet that's causing water to run down a pipe behind the affected area? Or is that too far fetched?
Water will indeed "suck" in through any tiny cracks. Capillary action!
Infact, people forget that grout (unless epoxy) isn't waterproof but will soak water up and pass it through to the background.
Worth checking for leaks - maybe cut out the wall behind?
Are you 100% sure there is no leak coming from the shower outlet?
To me it looks like water has jetted out at a downward left angle from the outlet and trickled down the grout lines. Only asking because similar marks I have seen like that in the past in almost the same position have turned out to be rust..... maybe check the internals of the shower outlet to make sure there's no corrosion of some kind and try a rust cleaner (if you don't want to spend anything, you could try white vinegar) to remove the stain?
Worth a go before ripping the lot out. I could be completely wrong but just saying what I see.