Is this the kind you are talking about? I did a search for Cheminee - is this in Australia? What do they burn?

Ah, I wouldn't think so. Photo B is the external side of the chimney, which would have originally been outside the house (the external wall). So i'm guessing your living room was added onto the house at a later stage. So it was never designed to be a double sided fireplace, like some are. And yes, it is a structural part of the chimney. By the way, your bedroom fireplace is a beautiful original mantle, I wouldn't touch it.

I am no expert but as far as I know, the only way to have the fridge flush and functioning successfully is to have an integrated model.

I take it this room is the living room, and that you definitely want to have a fireplace for ambience? I would first consider which would be more useful, a fireplace or some bespoke joinery such as the floating entertainment unit. Also, how long do you plan to live in this house and do you need to think about future resell? What do buyers want/need more, ambience or storage? I’m all for having what suits you and your family best. If you decide to keep fireplace, I would build out the wall in order to accomodate a gas fireplace with a more substantial surround to suit the style/period of your house. You would lose a section of that wonderful Axminster carpet, alas. Love it...we had very similar one in a previous home. If the room is large enough, perhaps you could also have a floating unit built at the same time, if budget can stretch. I am curious about the carpet...is it only in this room or throughout much of the house?