The twin-&-earth -- "T&E" -- is officially designated 6242Y, and the 3-core plus earth is 6243Y.
The T&E with twin red conductors doesn't seem to be used that widely. It's available only in the smaller gauges for lighting switch drops, but most of the time the regular red/black is used (Regs. require the black to be taped or sleeved red when used as a switch return).
