I'm pretty sure that I noticed a purple wire at the back end of my 110, when I was looking for a wiring fault, which wasn't connected to anything else.
It would seem to be a spare permanently live and fused auxiliary feed. I have no idea which fuse it's connected to, or how much current it's safe to use.
It hides behind the blanking panel inside the body on the drivers side. That's the panel that is on top of the seat box at the level of the indicator, if that makes any sense.
I'd suggest having a look in there.