Did the contractor fit the isolator and forget about the submain (or the submain neutral at least)?
No, but you'll love the artistic element of his work
OK, so this is what was in the box :
So now we see that there's an extra terminal in there that the metered live has been taken to, and then from there to the Henley on the left where it's split for the two boards. The Neutral for the submain goes in on the left, loops right round the box, and is shoehorned into the bottom of the neutral terminal - the contractor had a bit of a fight getting it out !
Anyway, after a while he was finished :
Ignore the grey cables, they're mine to sort out in due course. The blue and brown cables are his handywork
He said he couldn't get the live cable in the top of the box
He did spend rather a lot of time with the seals - he said that he's required to seal everything he "touches", so has sealed the load side of the isolator and the Henleys. But after some time spent fiddling he could not get a wire through the hole on the cutout itself - so put on his notes "sealed with tape". Not that I would ever consider removing that tape
A little about the contractor. He's an ex meter reader, who seeing the writing on the wall took up the offer of training to go off and fit meters.