Mains, PSUs and other goodies.

[Rogue]

ah ha ah . .bet there's more bloody timber in them 2 bench's than the whole floor . . lol

Probably - if the floor ever collapses the benches will come out intact, and that's the important thing. The only thing they contain in greater volume that timber is woodglue

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? If I can get something with a bend in it then I can find the bottom and work out the height as well.