I don't think so - it happens from +1C. It will probably start after much cranking at this temperature, but anything lower it won't. It just keeps cranking and I don't want to kill the new battery.

I'm in the UK so it never gets colder than -4C.

Other mechanics I have contacted did mention that the fuel pump might be too weak to pump diesel gel.

That would explain why when its warm it starts like there was never a problem.