There's a lot of documented case of motorway chargers not working.
If you bought it on finance it might be worth contacting the finance company about your issue.
The air suspension sensors can be recalibrated but I shouldn't think you'd need to do that with the work you've had done.
https://www.audizine.com/forum/showthread.php/966127-C7-S6-Level-Sensor-Calibration
I'm based in Leicestershire but my A6 has been off the road for 2 years as it needs a replacement engine.
There's simply Audi in the new forest. There's a German car show coming up at the British motor museum at gaydon.
Correct that's where the CCM is. It would explain why the keys aren't working properly. Be careful of your electric windows as I suspect they might not work properly either.
If swapping the CCM you'll need one that's got the identical part code.