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Tiling directly onto a wall ...
Depends on the tile and the wall and the substrate.
I stripped all the plaster off the brick and plastered with a thick cement reeder - the tiles (which are literally the cheapest you can buy) have been up for years (without grout 😖) and there have been no problems.
When I removed some to change the mixers and fit a hand held shower they were stuck on forever.
The repair after the plumbing was also cement render - but I tidied it up with bonding to get a smoother surface for tiling onto.IMO outside walls should always be cement render - especially next to a window.
Impressively neat tap alignment, very jelly, I forgot about tap alignment (with tiles) when planning mine.
I thought tiling straight on t oa wall was a big no no though? Especially around the wood window (which looks very nice btw).