On 11 Jan, 15:01, John Rumm wrote:

It all sounds a bit over complex...

I would have thought sticking a wood batten between a couple of joists,
and arranging the pipe to run horizontally to the batten, and then use
an elbow to pop down through a hole in the batten. The end of the pipe
fitted with suitable fitting to take the shower pipe at about finished
ceiling level, and screwed to the underside of the batten.

I agree - this is pretty much exactly what I did with a Hans Grohe
raindance shower head in our shower room, except the batten went over
the top of the (attic) joists, on which the feed pipe was clipped,
then it went down via an elbow and into a straight tap connector
fitting (this made it easier to get the tap connector at exactly the
right level compared to the ceiling. The showerhead's chrome ceiling
pipe then just screwed into the tap connector, with the (supplied)
chrome ring hiding the joint.