On Tue, 31 Jul 2018 06:19:12 -0700 (PDT),
wrote:

Admittedly when I cut through the cable in the bedroom ceiling there was
quite a lot of arcing, and it was rather disconcerting seeing the sparks flying about overhead, and the 30A rewireable fuse didn't blow

Takes a lot of sustained current to blow a 30 A wire fuse in a short
time. An MCB would have tripped using its magnetic rather than
thermal mechanisium.

Replacing wire fuses with MCBs is a good move and produces a
reduction in fires or WHY. RCDs are also a good move. But I can't
help thinking that AFD's are steeping over the line drawn by the Law
of Dimishing Returns, particulary on an installation protected by
MCBs/RCDs or RCBO's.

--
Cheers
Dave.