My Golf Mk6 GTD wouldn't start this morning.

Last time I drove it was yesterday and had no problems. This morning, I'd turn the key and it would make a clicking sound and flash all the dash lights at me and give me various error messages. It had "Fault Stabilisation Control" twice, then the next time I tried it said "Error: Airbag" and then "Move selector lever to position P/N" before I gave up (was in P and I was unable to change it to anything else).

Called roadside assist (since it's only about 7 months old). RACQ dude took one look and said it was the battery.
He hooked up his jumper leads and it started first time! (Some of the warning lights were still on, but he said they'd go away after a few starts).
He told me I needed to get hold of a battery charger. No need to buy a new battery.
So I'll be borrowing one today and charging it overnight.

Seems really strange though... how it's only 7 months old and the battery has gone already. I certainly didn't leave any lights on to make it flat.
You'd think it would say "Flat battery! Feed me!" instead of giving me unrelated error messages...