I planned on flush wall mounting Klik 6A sockets - lights, smoke/heat,
em-light.

Ceiling Rose KLIK will not seal against a conduit box (they wobble),
requiring either a deeper sunk box using plaster as the mating surface
or a surface mount pattress. AX KLIK however are a 1G faceplate so fit
standard backboxes.

It just occurred to me that Klik lacks shuttered pins - so industrial/
commercial only?

Table lamp BS546 sockets DO have shuttered sockets conversely - so
domestic legal.