First thing I thought was - the cpc is switched, and the box isn't earthed.
Then there's the lack of sleeving, lack of cable protection & restraints and the unblanked hole already mentioned.
But regarding the last, judging by the state of the inside I'm not 100% sure that the cover was removed just for the photo - maybe that's gone awol too.
On the grand scheme of things we can probably overlook the exposed L&N conductors on the incoming side, but should we overlook the fact that the load cable is smaller? What's the supply fused at?
I can picture the design of the switch - shouldn't the ON/OFF indicator be attached to the operating toggle?
And there's a crack in the switch body.
And generally it doesn't look like the sort of environment where there should be unprotected cable clipped to the walls, but then again it might just be that Mrs Sheds works there as a cleaner....
Reminds me of my own TP nightmare. In this case, the "earth" was actually used as as second switchwire for a sink/bath immersion, meaning the heater had no cpc:
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