Car is still with MG. They have done a few updates and they have asked for a technician to take it home over night to give it a longer test drive. If the update has worked I should get the car back tomorrow. Will update once I get it back.
Minor update. The car is in with MG in Milton Keynes. Had a call today to say they have gone through everything they can their end as there are no fault codes coming up. They are now in contact direct with MG China and going back and forth with checks as they say the car shouldn't be doing this. Fingers crossed they will have got to the bottom of it tomorrow and will update
UPDATE After 3 days of back and forth with MG head office I have the car back, which has had a few software updates applied (unfortunately I didn't get to speak with the technician so not sure what exactly was changed).
I took the car out on Saturday morning with around 45-50% charge and air temp around 2c and had no loss of power as I would have had before.
I did drive it fairly hard (down to 2mls per kwh) and got it down to 12% when I got home at which point there was some drop off but I'm assuming this was down to there being no range showing. I would usually be driving it fairly economically by that point anyway so I wouldn't really know if this happened anyway.
So it looks like the issue HAS been fixed. As the weather is picking up I'm not sure if I'll know 100% until next winter but fingers crossed it's all good so far!
I am popping back as the wing mirror (which is now working again ?

) so I'll see if I can find out what it was they actually did. If I do find out I'll post another update.
It could be me having driven the Zoe for nearly a week but it feels a little bit more responsive. But that could just be in my head.
Happens with ours too. If I know it’s going to be cold I just keep it fully charged. Once below half battery power it’s not a happy bunny
Not sure if the notification will pop up on my post above but looks like there is a fix via a software update so I'd have a chat with MG at its next service. They can contact Glyn Hopkins MK as that's where I took mine if it helps. As the engineer I took out to demo the issue said "it shouldn't be doing that". So it is an issue with the car.