On Sunday, 4 April 2021 at 15:34:12 UTC+1, Brian Gaff (Sofa) wrote:
Are you worried about the insides of corners etc? How is it assembled at
corners, surely not like a water pipe with fittings? I don't think I've ever

It's been used like the plastic oval stuff - straight runs in plaster. No corners.

Experimentation in the garage says 2x1.5mm T+E just about fits, and a single three core is easy - provided that the cut end is reamed out properly.