They had an offer on at the local screwfix a few months ago for
"rewire packs" - basically a bunch of assorted sockets / switches /
back boxes for about £50.

I've since had two of the light switches start arcing internally, one
with about 250W of load, the other with a low energy 11W lamp. I've
had this on a one-gang and two-gang.

The cable connections themselves were secure, it was arcing inside the
switch mechs at the pivot point of the metal "toggle".

Just thought it was worth mentioning in case any of you had used them
(Screwfix have been notified) :-}