Rear parking sensor control unit location

Reverse light works correctly.
Problem is with the parking sensors - the buzzer has been checked and confirmed working.
The problem is with the control unit as there is no indication of the unit operating properly.
Can't find any blown fuses relevant to reversing.
Need to know where the control unit is in order to replace it.

Thanks in advance - Graeme

Behind the passenger side carpet in the boot. It's stuck to the back of the metal panel with velcro pads. I have a spare unit if you need one as well.

Thanks Rick, can you tell me anything about the wiring leading to/from the unit?

Usually earthed to the chassis. Power from the reverse light. Then 4 wires going out to each sensor. That should be it