Replacing bathroom light pull - old colour wires

[cowgomoo]

I took my old bathroom light pull switch to replace with a new one, but the wires were too short to reach the terminals on the new fitting. I bought a junction box to put up in the loft and some new 1mm2 twin and earth cable to extend the length - Brown, Blue and Earth.

The original cable to the switch appears to a single cable red, red and earth. Have I got the correct cable (Br,Bl, & E) and how do I wire it into the old colours in the junction box?

[lecky1]

To replace the pull switch and associated wiring,you need to find which of the 2 original red cables is the live feed to the switch.This will connect to the Brown of the new cable.The second of the original red cables will connect to the new blue but this should be marked with red oversleeving or red insulation tape to indicate that it is also a live cable albeit a switched one.This cable should then go to the light fitting.
The earths should be connected together and the bare earth wire sleeved with green and yellow oversleeving.