Notch up another GTi with a dead OEM battery. No warning, just >click< and nothing else. A fully charged jump-pack failed to do the trick and another running vehicle was drafted in to achieve a start. I went straight for a replacement owing to an urgent need for a reliable car - £200 from a local garage for an Exide 70Ah AGM battery so not as bad as dealer prices. Mine is on a 2016 plate.
My "dash as Christmas tree" experience was a little different as after all the usual lights went out, following a short drive, the traction control light came on, followed by an exclamation mark symbol. It only went away after I'd disabled and re-enabled traction control via the menus. All ok eventually but as others have remarked, seeing all those warning lights would have been a bit of a shock had I not been prewarned by this thread.
And yes, that means I'd been reading this thread and wondering about the state of my own battery, even though it hadn't given me any trouble - and then bam; next day it failed... Gotta be a word for this form of fate ;-)
Cheers
Andy