I think from what you say that you will have an a light grey wall color from the high railing down, darker grey above the rail, and white on the ceiling? You would paint the fireplace surround the light grey color (Cornforth white) but paint the remainder of that wall darker grey (so below the rail as well), with white built-in cupboards on each side...is this correct? If so, it seems there would be a "stripe" of the darker grey around the room on the upper wall, not sure how this would look (a photoshop mock up would help, but I don't have that skill). I like the Cornworth color and think it looks great with white. I would use only the two colors - white for the trim/rail, the fireplace surround, and the ceiling, and light grey for the rest of the walls.

Hello th0m45, Definitely leave them soot and all if you want it to look like a fireplace but you don't want to use it.. (I'd see if you can do) but some people don't want to or can't. This doesn't mean you can't have the aesthetic... Buy a Swan basket freestanding rather than dogs.. that is big enough for the opening.. Then fill with logs.. You could have a slate hearth made to fit and then paint the chimney breast a contrasting colour so it stands out and then add a mirror. You can even add a mantle with two brackets and a large piece of wood as a very make do idea.. Here's a pic of mine as an example.. The original black and white surround was ripped out bashed up and thrown into the recess which I found (heartbreaking).. and in it's place it had a thirties thing put in...before I bought the place! So although it's a working fireplace (now) it doesn't have all of it's original features - I did though open it up and get it working again.. All I need now is a marble surround. or make that two as it's the same in the bedroom!. : ))

The colour of the quarry tiles and the brick will really complement grey sofas. Personally I find the dark red stain of the wood and the mantelpiece a bit unappealing. If those could be clad, or replaced with more earthy, old looking natural wood it would help. I would also skim the ceiling and fit new wall lights and led downlighters.

Jade sounds amazing! I would definitely go with a bold colour and certainly not cream. I think the jade would pick up the colours in the sofa and create a real impact. Not sure purple would work as well as the jade. Ours is white but only because we have a dark navy blue wall, but if I had a pale wall I would love to paint it a really striking colour.