I have actually wired up consumer units using a plug and socket, the idea is you can unplug the consumer unit from the DNO supply and instead plug it into a generator. However this brings us back to
“consumer’s installation” means the electric lines situated upon the consumer’s side of the supply terminals together with any equipment permanently connected or intended to be permanently connected thereto on that side;
this is what the government says should be inspected and tested in an EICR note the 'or intended to be permanently connected' that would likely cover a consumer unit which can be unplugged, and possibly also the boiler, and immersion heated. I know boilers are normally fitted onto a plate, so to remove a boiler and refit is not really that hard of a job, and all pipes are screw fit rather than soldered, and an immersion heater only screws into the cistern, and I know my father-in-laws house there was a blank where it should have been, it was removed when the solar panels were fitted.
However the home needs to be inhabitable, so if there are gas lights in every room the electric lights could be disconnected, if there are fire places then central heating could be disconnected, and I suppose in my mothers house to have removed the fuse in the FCU supplying the garage one could reasonably say no electrics to garage.
So the question is what electrical power is required to make the home inhabitable? what is the minimum that can be installed? When rewiring his house my son lived in his house with just two 13A sockets, everything was on extension leads until nearly completed, which took him around a year, while his wife and children were at his mother-in-laws that was not so bad, but when they moved into the caravan in the garden it was not really good enough, and we did have words about it.
And we have the requirements for a caravan in BS 7671 and that is always plugged in, one could hardly say the caravan passed the EICR as where tested in storage there was no power.