The bit in the second photo is for an earth. A lot of the earthing requirements have changed, ask in the sparks section for up to date info on the regs.
The bottom picture is a bracket purely used to hang the bath from during manafacturing.
As for the earth bonding I'll leave that to others who will be more up to date on the electrical regs
It is not earthed, but bonded.
Very few houses have the bonding installed correctly.
Technically speaking, it is an electricians job, so officially, your plumber was not allowed to change it. Chances are the old bath was not bonded as there does not seem to be a loose cable, so probably nothing has changed.
If it gives you peace of mind, get somebody to run a wire from the visible clips to the bath.
To make sure it all works, you need a specialist (rather pricey) tester and only an electrician will have those.
Bear in mind that if you have it done by an electrician, he will probably tell you there is more that is not up to spec.
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