If you go to a reputable car part supplier like halfords it will ask you for your registration and suggest a battery, so for my 2012 Qubo Trekking (Snap!) it suggests Halfords EFB013 for £140. You will get the same service for a decent small independant shop as well plus some will offer a cheaper alternative if you do not use the start stop function just make sure you don't or the battery will not last! Or you can get the number off your battery and do an online search. I keep putting off replacing mine as they are so expensive.