Adding to my Home Automation thing that seems to be going pretty well
so far (good lockdown project g) and with my interest spiked by mate
getting a 3 way TP-Link smart trailing socket (KP303) that works well
in Home Assistant, I was thinking of making my own 4 / 8 way versions,
the 8 way for powering all the TV / HiFi stuff, much of which is not
used most of the time. [1]

I was thinking of using skirting / dado trunking for the 'boxes' with
1 gang accessory plates to take single 13A sockets and with a couple
of end caps (glued on with PVC cement) and possibly some small bits of
cover between the accessory plates (depending on make / model
possibly?), I should be good to go.

An 8 way could be two 4 ways fixed side by side.

The electronics are easy with an ESP32 WiFi micro controller driving 1
or 2 opto-isolated 4 way relay boards, some mains flex, cable
restraining grommet in a end cap and 13A plug (with low value fuse)
and I assume it would be ok to wire it internally with singles? If so,
what CSA would I need (/ safely get away with as officially as any of
this would require), working on the basis that no outlet would be
drawing any real current and the relays themselves probably aren't
really good for more than 5A (although they are (Chinese) 'rated' at
10A at 240v (SRD-05VDC-SL-C)).

So I'm also looking for recommendations on the trunking. I will
probably only need 1 off 3m(?) length of the actual trunking and cover
but will need a few 1 gang outlet plates and ends ... and looking
around, any can be quite expensive so I would be interested to learn
what could be the best VFM brand for all of the bits that I might be
able to pickup from one of the normal suppliers?

eg. TLC do the Univolt 100mm x 50 line:

https://tinyurl.com/257updnu

Where the 3m trunking is only 17.40 / 3m length but the 1 gang
accessory boxes are £2.40 (3+).

Similar pricing with Toolstation Kestrel / Merlin lines but I have
seen others with a lighter 1 gang accessory plate that was under £1
but the trunking was more expensive.

Cheers, T i m

[1] Measuring the power consumption of a commercial 13A smart socket,
I couldn't measure anything when it was deactivated but .6w when it
was active (relay pulled in). Considering the sort of thing I will be
controlling will either generally be mostly off or mostly on, by
building my own solution I can wire each socket to the NO or NC
contacts on the relay and therefore do what minimises the overall load
the best. Some devices might only be powered up now and again whilst
it might be handy to be able to remotely reset other things that would
otherwise be on 24/7 [2]. Or maybe de-power them on a timer or other
household activity (like there may be no point leaving the TV on (or
on standby) if we are generally in bed between 01:00 and 07:00).

[1] Like my Ricoh printer needs power-cycling after a firmware update
and it's not that easy to get to the power switch or plug etc.