I kind of agree with the workshop you used that the problem was a prime candidate to be caused by the TIPM unit. This is basically a fuse-box, relay-box and electrical control unit rolled into one and, when it fails, it can often cause the problems you’re seeing all happening at once. This unit performs a very similar role to the body computer in other makes and models and it’s used to allow various functions of the car to talk to other components and functions.

I understand that the new TIPM hasn’t fixed things, but faults with these units are not uncommon and it wouldn’t be the first time a brand new component has been faulty before it has even been fitted. A good check would be to try the TIPM from a car you know works properly and see if that fixes the issues. Certainly, the random and grouped nature of the faults points to the TIPM in a big way. If it really isn’t the TIPM at fault, I’d start looking for a bad earth somewhere on the car that is causing the mayhem.

But try this test first. Disconnect the battery and leave it overnight. Next morning, reconnect the battery and see if the problem has gone away. It’s worth a try even though the fix may not last indefinitely, but it’s simple and free.

It could be that the camera is covered with crud, and only needs cleaning, or it could be a fault with the camera itself or maybe the wiring.

With local production shutting down the big-car choices are getting fewer and fewer, but right now you can still buy a Calais if that's what you like. You can also buy an equivalent Falcon or Toyota Aurion. There are more expensive cars, from the likes of BMW, Mercedes-Benz and Audi etc. that would suit, but they come with a much higher price tag than a Calais. Others you could try are a Skoda Superb, a Honda Accord V6 Luxury if you're prepared to give up a little in size, and there's also the Chrysler 300C.