Originally Posted by X5Sport

Actually had to get one ourselves over Xmas as an emergency so it came from Halfords. There may be cheaper suppliers though at about £30 less, but we needed it there and then. It was an HSB019 in Halfords parlance, Bosch Silver Plus S5 series. Took me about 30 mins to change it.

Labelling on side:
12V 600 402 083
830A CCA 100Ah
0 092 S50 130 = Part Number
According to the Bosch Catalogue this = S5 013 Battery
Battery can be vented at either end and they supply a plug to go in the other end vent hole. Works a treat. Turned the steering left/right lock to clear the warning lights and away we went. Didn't even lose any memory settings as I waited for the car to go to sleep, then did it - result

There is an AGM Version the S6 002 which is a 95Ah/850CCA but it's a lot more expensive. Comes with a 6-year Warranty.
0 092 S60 020