Parking sensor buzzer location

[Nick Jones]

So.... VCDS says that the reason I get one long irritating beep (from the front) and no working parking sensors when I selector reverse, is because the rear buzzer is broken.
Seems a bit unexpected, but before I can test/replace it, I have to find it. It doesn't appear to be obvious so before I go ripping trip off at random any clues? Or do I just need new glasses?

Thanks

Nick