Jetblack,
The pipes will expand and contract due to them heating up and cooling down when hot and cold water flows.
This could cause your plaster to crack if there is no allowances taken for this. I put plastic conduit over them when I install them but they are already fitted so buy some plastic piping that is larger than your pipe work, split it open and clip it over the pipes before you plaster.
KB
Is there a cover plate that goes over the valve mechanism? If so just tile such that the edge of the tiles are just under cover plate when fitted. Silicone cover plate to tiles.
Don't try and fill the hole. 1. Hot water will come on, valve will expand with heat, valve will push against filer, tiles will pop off or crack! 2. One day you will need access to the valve.
It doesn't matter that thee is a cavity behind cover plate and tiles.
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