Can't see the room layout, but if you keep it, it could be a nook for a sofa or chairs by the fire on a cold night, with a rug in front. Definitely have a mirror on the mantle. Think about walls and rooflines before you do anything. Or if you've got lots of cash to splash, take it out as it may serve no purpose with a heatpump in place. Replace roof tiles, internal brickwork.........you see what I mean, just saying......

strip part of the brick and mantle back to orignial if the exposed colour lines up with the room, strip the whole thing. Looks so well crafted not to pay respect to the past

The stained glass windows seem to be at odds with the exposed brick, but probably match the original part of the house. If the stained glass windows are giving privacy from an overlooking neighbour I would keep them, and work to make the brickwork more like the original part of the house, so it seems less incongruous. This could be done using a traditional wet plaster or solid plaster technique, which you would need to complete befor your gas insert fireplace is positioned. I would finish it of with a traditional timber fireplace surround and mantle piece, which would be the focal point of a more contemporary room, but link in with the original architecture. Best of luck, Dr Retro of Dr Retro House Calls

You have a complex set of requirements that won't be adequately addressed in an online forum of opinions. In addition the photo of the style of kitchen that you like is in a much larger space than you have available, and the size of that kitchen contributes to its presence. Without borrowing some space from adjacent rooms for a wider, larger kitchen then I would consider a G-plan with the end of the G being bench height seating with half the stools with their backs to the view, and the other half with their backs to the kitchen, as in this photo. I would engage a design professional to visit, take your brief, measure up and come back to you with a few concepts for the layout. Think hard about how important the symmetry is to your kitchen as it can really hamper creative solutions that are outside the box. It is still possible to have a Hamptons style kitchen, that has presence and is of a formal nature that is asymmetrical. The rest of your home is not symmetrical, and forcing a symmetrical design into a pre-existing space only ends in compromises to the functionality. A good design professional (not necessarily a kitchen designer) will look outside the three walls that are constraining your thinking and options to create an elegant solution, but you will need to pay for this creative service. Best of luck, Dr Retro of Dr Retro House Calls/Dr Retro Virtual Visits.