In article ,
wrote:
On Wednesday, 24 August 2016 15:51:46 UTC+1, David wrote:
Does the fact that an electrician signed off this installation imply
that the rest of the system was safe at the time of the upgrade?

No.

The installation (or minor works) certificate only relates to the new
work stated on it.

The electrician should not have *knowingly* reconnected *unsafe* wiring
to the new consumer unit, but that does not mean the wiring was safe. In
particular there may be defects which were not visible and not apparent
on testing, eg bare live wires under the floorboards but which
nevertheless pass an insulation test. Old rubber wiring can also pass an
insulation test if not disturbed, but can crumble at a gentle touch.

"upgrading the fuses from wire to plug in RCD," doesn't quite make sense
either.

It does if it was a Wylex CU. They were designed with that in mind.

--
from KT24 in Surrey, England