Mazda battery....

[miniblob]

It never rains......

So I knew this car was going to need a battery before winter, just not got round to it!!!

Car is a 2012 Mazda 3 2.2d sport (150)

Does anyway have any way to find out what spec battery (ah, cca) this car should have?
It has what I presume is the original battery, all tucked in, no visible labels/markings!
I've taken a couple of measurements and had a look on ECP, etc, but they all list quite a few different batteries for this car - none of which match size wise and all seem to be different specs!!!
I want something decent, as it's the other half's daily for commuting and moving the little boy around!!!

Also - any idea if I'm going to encounter/cause any issues, taking the battery off this and sticking on a new one???
I don't really deal with stuff this modern!!!