It happens that GB formulated :
This particular one, you lever off the hot/cold indicator button on the front
of the tap, and the grub screw is under there.

I'm more interested in what you do when you've dismantled the tap? There's
nothing to tighten up. Maybe, put a new cartridge in, but that's going to be
most of the cost of a new tap?

To be fair...

I have just noticed I fitted the very same mixer tap to our bathroom
wash basin (shows how little attention I pay), this was some ten years
ago and it is still working absolutely fine - no drips at all.