Just an update on the original issue … MG have run diagnostics on the 12v and there doesn’t appear to be any long term damage as it is still reporting that a good near new battery.
Alas however, MG cannot access any of the vehicle’s diagnostics to be able to find out what software levels are on the car, whether there are any error messages etc etc. Garage now awaiting a ‘fix’ to enable their diagnostic tools to be able to ‘see’ my car and find out the state of play. (Apparently it does on all their other cars in the garage when mine went in).
The garage has also said that I may never find out what has caused the sudden drain of the 12v … how re-assuring!!
Just as a point of interest for some users potentially… before the 12v went dead .. I had no radio and the Nav would ‘brick’ ie the audio directions would continue, but the visual display directions would freeze. After the battery died ie was effectively disconnected … both these functions now work without an issue !
I don’t want to suggest this as a fix for those that have similar issues with their infotainment system as I don’t really know what I am doing with car electronics… but I did find it an interesting consequence.