Interesting.
Thanks for the replies.
Like I said, most of the fault codes I saw said low voltage or similar. I'll check if my C110 can register the battery.
The fact that it's had an alternator and battery would indicate that the garage were chasing a drainage fault but not diagnosed it correctly.
I put my ctek on it for 4 hours yesterday to see it I could boost the battery but I don't know what happened as I had a few beers and lost interest..