Jo King wrote:

Fitting a shower want to hide the pipe behind plaster can I use
compression fittings or has it got to be soldered joints. or would plastic
flexi pipe connect to the original copper.
Thank you for any help.

I use copper with soldered elbows where the pipes turn to come out of the
wall, or plastic with a compression elbow. In either case test for
water-tightness before plastering and tiling in (obviously)