12"/30cm is correct as per the manual IIRC it's to allow an estate boot to open if parked next to a wall

Mine was a bit over-cautious but go used to it, then last week packed in alltogether and nearly hit the neighbours car!

I get one continuous beep on engaging reverse then nothing on the display - good job still got warranty left.

Just fit a tow bar, reverse until you feel a bump then pull forward an inch..........

Be careful about reversing up to metal/concrete posts. The beeping can actually stop when the posts are between sensors and so close to the bumper that the sensor can't "see" it. When the beeping stops you might think that it was a false alarm and carry on going. False alarms sometimes happen when the ground slopes up behind you but not so much that you could actulally hit it.

Another one to catch us out is when there is a barrier with an overhang and the overhang is above bumper level.