Ok found it.
This may already be known but all the red/whites are soldered together at the bottom next to the starter relay/main fuse.
Mine had corroded in the soldered connection and when I changed the fuse the one that feeds the lights had broken off but still been touching.
Bit of a stupid place to have 8-10 wires soldered together right where road salt will get in and corrode them, it'd have been better to have a sealed connector like the rest are!
Anyway I've now got to get all these wires soldered together with enough length to still reach.