Mains, PSUs and other goodies.

[John S]

I wonder, is there likely to be enough of a gap between the floorboards that I can poke something thin between them to find the edges of the joists to work out the width? .

Measure between the heads of the floor board nails ?

[Rogue]

Measure between the heads of the floor board nails ?

For the distance, yep, but I think the issue was the actual width of the joist unless I misread it? But measuring nail gap is also going to be done.