I guess my question then is: is there any difference between a permanent "hardwired" circuit and a non permanent "off a plug" circuit in terms or regulations?
As I understand it (I am not a lawyer).
There are two major questions. firstly is something part of the
building at all? and secondly if it is part of a building is it notifiable under the building regulations.
If something is fed from a plug, not fixed to the building in any way and is able to be easily moved out of the building then as far as I understand it's not a part of the building and therefore building regulations are not applicable to it. There may be other laws of course, if you sell the item you would have product safety legislation to contend with and if you allow it to be used in a workplace you have the electricity at work regulations to contend with, but I don't think there is any law preventing you constructing arbitrarily dangerous electrical equipment for your own personal use.
But if you fix a complex arrangement of electrical devices to the building, then I don't think you could argue that it is not part of the building merely because it is fed from a plug.
The second question is whether it is notifiable, and the answer to that depends on what part of the UK you are in. England and Wales used to have the same rules, but the rules in England were radically changed while the old rules remained in force in Wales. I have no idea what the rules are in Scotland or Northern Ireland.
Particularly worth noting is that the old rules (still current in wales) and new English rules work in the opposite way, under the old rules all electrical work in domestic premises is notifiable except for a list of non-notifiable activities. Under the new rules only specifically listed activities are notifiable. Since the old rules are still in force in wales, and since a lot of advice on the internet was written based on them I think it's worth discussing both.
The old rules were quite complex, some activities were exempted from notification in any location, others were only exempted from notification if they were "not in a special location," and others still were only exempted from notification if they were "not in a kitchen or special location and does not involve a special installation".
In particular "Adding lighting points (light fittings and switches) to an existing circuit" and "Adding socket-outlets and fused spurs to an existing ring or radial circuit" were non-notifiable only if they were "not in a kitchen or special location and does not involve a special installation". Relavent to the topic at hand one of the "special installations" is "Outdoor lighting or power installations".
The guidance in the approved document (
https://gov.wales/sites/default/fil...lations-guidance-part-p-electrical-safety.pdf ) says "Detached garages and sheds are not special locations. Work within them is notifiable only if it involves new outdoor wiring" but that's only "guidance" not part of the law itself.
On the other hand work on "Prefabricated equipment sets and associated flexible leads with integral plug and socket connections" was exempted from notification as long as it was "not in a special location,". The question then becomes how far "prefabricated" can be stretched, I think something made on site from arbitrary components is definitely not "prefabricated". The kits flameport mentioned with the socket pre-attatched but where you wired the plug yourself seem to be stretching the limits of the definition.
On the other hand the new rules in england have no mentions of plugs and sockets at all. All mention of Kitchens and Special installations is gone too.
It's worth noting that the building regulations lists of "special location" and "special installation" are much shorter than the BS7671 lists.
