I have bought a new ceiling rose for a light. The wires in it are UK pre-2004. There's one black, two red, one yellow, one blue, and two green and yellow earth. Where do all these go on the ceiling rose?
Often, electricians used ordinary black/red/green twin&earth for C but marked the black wire with red tape (to indicate "switched live")
You seem to have something nonstandard, perhaps a spur (therefore missing B) without an earth to the switch? You'll have to use appropriate methods to determine what is what.
See answer to similar old question https://diy.stackexchange.com/a/32251/2815