D4 dead flat battery - help please

[mondie]

Our car must have gone off me. After the recent handbrake failure it now has a stone cold dead battery. Had been fine until Saturday when it would not even unlock. Used the key to get in but found the car to be completely dead.

Is this normal for a battery to fail with no warning? The car has stop-start so I am wondering if it is a safety feature for the car to 'switch off' if the battery is too weak, but without warning is what I don't understand.

I will have the battery on a charger for all of today and see how it responds but it looks like I need a new battery at close to £200 Is it a simple changeover or is there a specific procedure for such a complex car?

Cheers all, Simon