I have to re-wire a light switch due to the cable not quite being long enough. The house was built in the early 70s and the switch currently has two strands of red/green to it. This is a straight forward replacement so a junction box in the loft and a new bit of cable is all that needed - there's not much thought invloved. I have some 1mm twin and earth (blue and brown). Is that OK for this? I remember reading somewhere that the core colours should both be red. If so, where do I get 1mm twin and earth with both the cores red? B&Q/Screwfix don't seem to list such a thing!