The backup camera being rather unfocussed and slow, I decided to add back up parking sensors. Chose a cheap eBay 4 sensor kit with display and beep signal. Painted the sensors to match the car colour. Started by identifying the red coloured rear back up light wire (see picture below) in the cluster of wires running on the left wall of trunk. Used a feed from that to power the sensor box/brain with a red wire. A black wire from the box connects to earth/chassis. All connections are usually well s