Heres what i do...
To get the positions for the lights, divide the length of the room by the number of lights in a row ie 3m long room with 6 lights in 2 rows: 3 meters divided by 3 lights= 1 metre
This is the gap between lights in that row
Then divide this by two to get the distance from the wall to the first/last lights so 0.5m
So you have
Wall_0.5m_light_1m_light_1m_light_0.5m_wall
Use the same method for the width of the room
ie 2 metres divided by 2 lights
so
wall_0.5m_light_1m_light_0.5m_wall
This gives you the most even spread of light across the room
Now you have your 6 lights marked draw round each one using the holesaw you plan to use as a stencil
Now on each light outline, using a very thin screwdriver stripped of its insulation, bang a hole in the centre and 4 holes round the edge in the shape of a cross (parallel to the walls of course)
If you hit an obstruction, ascertain which way the joists run and if nessecary move the whole row of lights to avoid that joist. You may then choose to move the other rows to ensure even spacing, this can be time consuming.
Once you have all lights in positions without obstruction and evenly spaced, then and only then, you may cut your holes.
With regards to the pendant, just take it off, mark the switch line using cut/tape/sleeving whatever (this is just common sense and its slightly worrying that you are asking about it) push the cables into the loft and reconnect them into a wago box. If there is no loft you may have to cut an extra 50mm+ sized round hole where the pendant was to push the box through which you then batten and refit the cutout.
This method is the one I always use and works well for me. It saves me jumping in and out of the loft like a chimpanzee on crystal meth. The downside is that there may be some minor making good to do on the ceiling but I always warn my clients that they should book a plasterer, decorator, industrial cleaning firm, carpet fitter and the fire brigade to follow me immediatley after any job I do, no matter how small.
For some reason not all of them find this funny....
