Reversing beeper

[sciteacher]

Hello. Again! My reversing 'beeper' has stopped working. I'd really like to solve the problem so I would be really grateful if anyone can tell me where to start looking.  Where are the switches that actually turn it on, for instance?. I assumed that it might be at the gearbox, but i did read elsewhere on the forum that there is some wiring near to the n/s reversing lamp.  I mention the gearbox because my thermostat housing has leaked in the past (well the Berlingo's to be fair ) which I believe might be over the  gearbox are and might induce some corrosion.

Anyway, any and all help would be gratefully received.

[jtr rhyl]

Mine in my 61 model was passenger side back panel in the boot, little black box, if memory serves me right. Just over 6 years ago.