I have separated the plug i.e unplugged the rear wiring loom from the car side, and the contact pins inside look nice and shiny. I can't see a way of looking inside each half of the plug if that makes sense, as i dont think its meant to be split. I might remove the rear loom from the car completely and see if i can find a wire that is not showing a resistance from the connection block to each of the three sensor pins. That might indicate a break. Also i can do it in the garage as its freezing out there. If this all tests OK, i might then cut that joining plug off both the car side and the other half on the rear loom side and hard wire it back together. If that still doesn't work (assuming as i had ticking from the sensors before fiddling with the wires) i can only assume its the wiring that goes in to the chassis. This is where i might have to stop and maybe get it re-wired from the control unit bypassing this. Does this make sense? I will take pictures and post them later before i snip anything off though.