The light grey cut outs being mentioned here are series 7 cut outs, in my experience working for a DNO previously, S7 cut outs were used where the supply was intended to be TNCS, however if the DNO has not put a PME label on the cutout, then it cannot be and must not be assumed to be TNCS, as there are reasons they haven't done it, and as the S7 comes with a pme sticker it hasn't been missed off because they didn't have one.
Only confirmation from western power or similar will confirm supply type.
if the supply is TNCS, then on the right hand side you can knock through the blank allowing connection and drill a couple of small holes in the front to access the screws.
the neutral cover shouldn't be waggled out with jiggery pokery, as it is supposed to be held in with a screw, behind the main fuse