I've dug more stuff out of the stash and found a right angle adaptor and a cut down 25mm spade bit.
However I am having difficulty making any headway through the joist, I think mainly due to the inability to get a lot of force applied to the bit. The pointy bit goes in but the spade part doesn't seem to want to get started.
If I point the drill down at a fairly shallow angle I could potentially drill a longer hole, but more easily as I can lean onto the drill with my full weight to encourage it to sink in.
Is there any reason not to use this method?
I am, of course, shamed by the lighting wiring where the holes look horizontal.
I am also puzzled by the irregular spacing of the 2" joists and the inclusion of a 2.5" joist roughly halfway across the room. Also the extra joist near the doorway. Still, 1930s house......
Cheers
Dave R