OTOH, if the OP is going to be having a lot of work done anyway, adding new circuits, splitting existing ones, replacing all accessories and adding extra new ones, replacing the CU, then so much of what is already installed will end up being exposed, worked on, tested etc that I question the point of shelling out for a formal EICR first.
If a full rewire is really called for then that will become apparent pretty soon, and if not then as long as he is using a trustworthy electrician who won't look for ways to rip him off, then the cost of the EICR will probably go quite some way to cover any incidental "gotta replace this bit"s that crop up along the way.
But as I say, it does depend on how much work is going to be done irrespective of the condition of the existing wiring.
If a full rewire is really called for then that will become apparent pretty soon, and if not then as long as he is using a trustworthy electrician who won't look for ways to rip him off, then the cost of the EICR will probably go quite some way to cover any incidental "gotta replace this bit"s that crop up along the way.
But as I say, it does depend on how much work is going to be done irrespective of the condition of the existing wiring.