The point about "correct electrical terms" is not pedantry, or electricians showing off their depth of knowledge, it's because getting them right, particularly when it comes to the issue of whether a wire is live or neutral, is of enormous importance -
possibly of life/death level of importance.
You've been "assuming" things about your wiring, such as where the circuit loops in, and what the functions of the conductors are based on an incomplete understanding of the different ways that lighting circuits can be wired. Assumptions like that can be very dangerous.
For example, if you decided, on the basis of your assumption that the black cores were unused, to replace your backbox with a metal one and replicate the connections you have now, then if your installation has no RCD everything would carry on working fine, but a dodgy earth could result in somebody being killed.
Mattayscough said:
Why would someone use two cables rather than one?
One reason could be because the lighting circuit loops in at the switches. Another reason could be that for this particular light a L&N feed was taken from the lighting circuit, to the switch, to then supply L&N to the light.
Is it ok to use the same configeration or should I replace with one 2 core and earth cable and label at the junction box the 'live' black cable that returns from the switch?
You cannot do that unless you establish beyond doubt that the black wires are not neutrals. If they are, then what you propose will stop the light from working, and if you pick the wrong cable to put inti the switch you'll get a big bang, a blown/tripped fuse/MCB and probably a wrecked switch.