When they build modern houses, do they generally put the ceiling plasterboard in place before the stud partitions, or after?

after I think.
At least that’s what we did and it all seems to be in the same place we left it.

I need to run a wire from a ceiling rose down a stud wall. Loft access will be tricky so I’m trying to figure out another way.

big spade drill bit and rip out a hole at the junction of the horizontal and vertical boards. Fill it up again later.

Yeah might have to do that. There’ll be a bit of wood at the top of the stud wall anyway and there’s no way I can get a drill in there. Even if I could uncover the top of it from the loft – if the ceiling plasterboard is continous I’d never find the correct place to drill from above.

use the spade bit to mine out any wood at the bottom of the ceiling joist/wall plate at the join of the two planes.

I’d never find the correct place to drill from above

Measure (in the loft) distance from ceiling rose, then copy measurement to ceiling from below. Amazed the wife when I asked her to watch from above whilst I drilled into the ceiling from below and was mm perfect in locating the hole….

Yeah, that won’t work unless I remove the suspended floor and all the insulation. There’s a chance I could clear an arm hole but I can’t do that. Stoner’s idea seems to be the only one, but I’m nervous about sticking wires in unexpected places.

either option will be found depending who built the house

as to which is best is six of one and half dozen of the other