[...]
That's interesting. Down here with Western Power they *won't* attach your earth. Instead they attach a short "tail" to the cutout and put a chunky black box on the end with chunky terminals in it. There's room in there for (if you need it) three additional cables of up to 25mm2 (I'm guessing there, but 16mm2 is a very easy fit). In other words, it matters not whether you've already done the rest of the work, PME can be "made available" for you to use when you're ready.
Up in Derby, they connected my dangling G&Y without bother.
Of course, for PME they have to do the external loop impedance test first - if the reading is too high they physically can't give you an earth and you'll have to make other arrangements.
Hwyl!
M.