Superb 3 - Rear Part Pilot Fault

Hi

Was hoping for some help regarding a problem with my Mk3 Superb Estate

For some months now it has had Rear Parking sensor fault.

sensors are all clean etc, fuses OK.

I disconnected and reconnected a connector under the bumper at Rear Right of car, and fault temporarily went away but soon returned.

Searching online and looks like there might be a ECU somewhere in luggage area on right or left.

Does anyone know where this is or where to find guide to strip down and access.

Any other ideas on things to check or try to resolve.

Many thanks

Arc