I am currently looking at buying my vrs. I have found 1 which has parking sensors.

What should the car do if they are fully functioning?

I have done a quick search but can only find info on mk2 systems.

Does it need a standard headunit to work?

No it's not linked to the headunit in any way, there's a separate speaker somewhere in the passenger side B pillar.

It should beep once when you put the car in reverse to tell you it's active.

Thanks il listen out for it when I next view the car

No it's not linked to the headunit in any way, there's a separate speaker somewhere in the passenger side B pillar.

It should beep once when you put the car in reverse to tell you it's active.

drivers b pillar

drivers b pillar

Really? The other wiring runs down the passenger side. Mind you I'm deaf in one ear, so can't tell where sounds come from.

yes i only know this as i removed a loom recently, the other loom is indeed on the passenger side, but the little speaker is in the lower b pillar cover