I'm hoping someone can point me in the right direction before I go
ahead and do what 'seems' best..

I'm refitting the existing shower-room which has a wall mounted water
valve with a hose-outlet to a handheld shower head.

I've got a Hansgrohe ceiling-mounted showerhead that uses a 100mm
vertical pipe with a 1/2" male threaded fitting. I'd like to use this
and intend to replace the shower valve, taking the outlet up to the
roof joists, to exit from the ceiling.

The fitting kit and instructions for the ceiling-mounted unit show
screwing the 1/2" fitting to pipework emerging from the ceiling. A
wall-fitting kit is also provided but this obscures most of the
threaded connection so isn't of much benefit.

I've been unable to find any ceiling-specific fitting kit for it, and
have been unable to find much detail on the plumbing detail of ceiling-
mounted heads. I was wondering about using a steel plate with a pipe
welded through it, tapping it at one end to take a feed from my shower
valve pipework and tapping it at the othersuch that I can pop it
through the ceiling and screw the showerhead pipe onto it. This would
give me a water feed AND take the weight of the showerhead, which is
quite heavy as it's large and well-made.

Does this sound reasonable? Does anyone know of any kits to achieve
this, or do I continue down the DIY route?

Many thanks in advance for any help,
Darren