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 http://diy.stackexchange.com/a/32251/2815

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

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, so you'll have to use appropriate methods to determine what is what.

See answer to similar old question http://diy.stackexchange.com/a/32251/2815

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 http://diy.stackexchange.com/a/32251/2815