Spurs to a 13A socket and a light switch need to cross a room in the
ceiling void between 2 joists. Then down the wall to the new socket
and a light switch.

Two Qs:

1. the ceiling void is clear (no thermal insulation) what is the ideal
way to route the cable? Ie clip to side of the joist?; Lay it loosely
on the plasterboard ceiling? or run it in mini-trunking or conduit?

2. both cables go down the wall (under plaster) in line to the double
13A backing box. The light cable is then to go 1m along the wall to
the switch. How should the lighting cable be run near the 13A backing
box? ie diverted round the outside or into the 13 A box and out
again?

TIA