Just a small point here. It has a 40A RCD and two mcbs. On the top of
the casing there are two terminal strips, one neutral and one earth. A
blue neutral wire is supplied that goes from the neutral terminal strip
to the "bottom" of the RCD switch. A small link is provided that
links the RCD with the two mcbs at the bottom of the RCD and mcbs.

The instructions are not that good. Looking at it, it seems the live
enters the RCD at the bottom as the neutral does too. Is that so? I
would think the live and neutral enter the RCD switch at the top and
out the bottom to the mcbs totally isolating them. Is the neutral wire
from neutral terminal to the bottom of the RCD switch to make the RCD
operate? That means the neutral across the RCD is bridged.

As the live enters the mcbs at the bottom the neutral must do as well,
with the out wores at the top.