> In the UK, if your shed is less than 15m^2 and is not used as living accomodation, no building regulations apply, and you can build it with screws, nails, or corrugated cardboard and PVA glue if you're so inclined.

In many US locations you aren't required to pull a permit and get inspections for sheds below a certain square footage either.

But that's not a free pass to build an unsafe structure. Using (non-structural) screws instead of nails is not a big deal for something this small that won't see snow load, but other things like mixing high voltage wiring and low-voltage wiring in the same conduit are a problem regardless of code.

Connecting something to the electrical system will also invoke code regulations, regardless of the size. There's no free pass for ignoring electrical regulations just because a building is below a certain size in the US, and I doubt there is in the UK either.