I think you could probably look at taking out that bit of red... Plasterboard? Leave the surround! Marble surround is fantastic and you could really open up the fireplace more actually.. You could take out the small grate and have the entire recess open and then buy stylish basket that is bigger even if you don't use it. You will see what the width is when you uncover the front. Just make sure the lintel is intact which I am sure it is... I had to add another to be sure. See image.. You see what I mean about being open.. Also I was not as lucky as you as I found my marble mantle piece bashed up in pieces at the back of the recess... I could not afford to replace it... So it's a piece of wood and two brackets! You have red above the picture rail, so I would keep that and paint the chimney breast a deep deep red that compliments what is already in situ. Also raise the mirror slightly or even replace with something a little bigger in height. : ))

The Edwardian fireplace is the correct proportion and age for the house. Hard to tell if it is actually original to the house or if it is Mahogany or Oak, but don't paint it. Wood has a beauty of its own if treated with a natural finish like Beeswax and the patina of age adds to the beauty. Certainly don't varnish it. One of the reasons it appears heavy in the photo is the oak surround on the hearth tiles. My advice would be to remove the wood hearth surround and install a wood floor in the room (perhaps oak and slightly lighter in colour than the fireplace butting up to the tiled hearth). This will will compliment the fireplace and ground it. You could remove the tiles (normally I would keep original tiles) but the cream and maroon colours in this instance do give an overall heaviness and don't particularly enhance the fireplace, however I would leave the tiles for the moment. The finished scheme should look classy and elegant with a neutral colour palette. If this is going to be a working fireplace than you may consider a grey slate hearth. This is the focal point of your room so getting it right is key. Wherever possible conserve original features. The 1930's fireplace on the opposite side would appear original and most likely installed in the 30's. It is charming but not proportionally correct for an Edwardian house. But because it tells a story and is original I would be loath to remove it. Selling it on would be tricky as the tiles will most likely damage when removing them. I would keep both fireplaces as they will both sit well in a neutral colour scheme with a wooden floor.

I know this sounds a like a silly question, but are you going to use it as an open fire? If so, you'd need to use heat proof paint, so colour / choice options are more limited. ( for the tiles ). Obviously you can paint the surround however you like. I think i'd keep the tiles as they are, depending on what other colours you wanted in the room. You can buy some great armchairs in mustard these days. It also goes really well with black. I too would go for a more traditional look with black and white smaller tiles.

As others have noted, it is absolutely stunning! So i am firmly in the no paint camp....I think I read a suggestion to see if you can lighten the feel by first changing the wall color in the side cupboards and see if changing the glass to plate glass - so agree! You could always take this as a first step and see how this changes things before going the full paintout path.