I'm on 1.4TSi petrol.

As my battery is the original 2015 I know it's worth keeping an eye on it, and mostly it sits between 60 and 80 percent even first thing in the morning, occasionally pops up to 90 after a long motorway trip

Just occasionally I look in the morning to find it reading "SOC 0%", which awakes a little frisson of panic, but it starts and runs beautifully with no problems beside the usual of the stop-start not always kicking in. I assume it is just a glitch, but has anyone else come across this?

I'm rather surprised your 2015 Octavia has the battery SOC indication available, is yours early or late 2015?

My 2015, MY16 just displays SOC--- and I understood the function was deleted around 2014.

Mine is early.. battery is week 6, 15.