Battery for Felicia Fun

With winter approaching I thought I ought to check under the bonnet of my Felicia Fun. I've only had it a few weeks so I'm starting to assemble a shopping list for my Halfords Trade Card.

The battery currently fitted is an "063" but looks too big to have been fitted without removing some assemblies.

Is this the right battery and if so aam I missing something obvious as to how it would fit? Spacial awareness isn't my forte (drystane dyking does my head in...), but this battery looks like a ship in a bottle.

Just asking the question for when that inevitable time comes to replace it, when it's so cold that your hands won't work.