I’m not aware of a ‘Sussex Group’ East Sussex and Sussex Downs are now one area controlled by Chris Unstead according to ghe news letter. This area is now named ‘East Sussex and Downs’.
Note: the owners club website has not been updated yet, I found the Kent area meetings too far away.
Ask Chris Unstead for the News letter showing the meetings and events, you will see that many meets are also held in Henfield BN5 9AD which suits me best.
Roy
I’ve managed to fix one of these before when it sounded constantly in reverse. It was caused by corrosion under the paint on a sensor. Because the paint layer had lifted the sensor thought there was something in the way; it was sensing it’s own paint! Scraping off the old paint then sanding off the surface and repainting cured it.
Oh, yes, I didn’t consider dirty sensors in my earlier replies.
My Focus sensors sound off if they get dirty too, just a wipe with my finger does the trick to fix it though. Flakey paint similar I assume. NewtoMX5 has dodgy wiring to contend with too though.
Roy
Mine aren’t painted. Black units on my black car. There’s nothing for it but to trace everything back to the unit when the weather allows. And that unit is very well hidden…
I’m surprised that they aren’t painted (possibly powder coated) because underneath the faces of these sensors are usually made of aluminium. One of the two I fixed was black in colour (it was an after-market kit fitted to an almost new, ex-demo car) and although the coating looked OK, on very close inspection the black colour had lifted very slightly and had white corrosion forming underneath. I scraped off the failed coating, sanded away the corrosion and found the system worked normally again so I used some satin black paint to protect the sensor. That was probably four or five years ago and it is still OK.
It’s possible that a previous owner of the OP’s car got fed up of the system sounding all the time in reverse and simply cut the power lead…these sensors are normally piggy backed into the reversing light, and his reversing light doesn’t work… Coincidence?
Ah OK. It’s possible they are painted. I just assumed they’re plastic black. The paint condition looks OK but I didn’t inspect them closely enough. I have been annoyed with one of them that won’t push all the way flush into the bumper, whatever I do. It feels like something is stopping it it from the other side.
The power wire did look like it was intentionally pulled off and the same tape badly wound back around where it was twisted over the reverse light wire. So yes, I also assume they pulled it off when it went wrong. The reversing light is working fine now and I’ve noted that the other side is a fog light. So it’s just a faulty reverse sensor function that’s the problem. It’s very strange that they have hidden the main unit so far back somewhere. I was expecting to find it closer to the light cluster rather than it going all the back towards the centre of the car.
NewtoMC5
It may well be that the speaker/buzzer is integral in the controller on the fitted init and to hear it properly it has been placed closer to or in the passenger compartment behind the seats??? or do you know it has a remote speaker?
The Hawk unit I have recently purchased has a speaker separate to the controller so if it’s not loud enough in the boot I’ll just move the speaker and mount it behind the seats.
Roy
That unit I posted a picture of on my last NC that had a separate speaker. It was situated behind the left plastic panel near the fuel filler pipe.
Most modern ones have separate speakers and some have an led display too but I am not sure about older units.
Roy
My car is a 2008 2.0 Sports bought in 2014 and I have a continues beeping like yours as soon as reverse is selected. The specialist garage from which I bought it said it is an aftermarket kit and the beep is normal. It does increase in intensity as I near any solid object behind.
Mine is well past the fuel filler pipe. I got to the corner behind the passenger seat and then gave up not wanting to pull any more panels off. I guess it’s there to make sure the driver can hear it because It’s bloody loud and constant even with my car facing open road lol.
That mastic sealant does not look factory fitted. Has it been in an accident?
I hope you’re not asking me since now I’m worried. Just bought the car last month. Do you mean the black sealant? Where does that go to?
I had black sealant around the same grommet where the wires passed through.
My sensors I have always believed to be factory fit, a professional looking job.
Well, that’s a relief 
I need some warmer weather to give mine a thorough check and get all the boot panels off to find the thing.