We are a stove showroom that offers a supply and install package. Myself personally, I would go down the fire board the chamber route on the sides, square off the opening as the arch is small or just leave the arch brickwork exposed and split face oyster slate the back of the opening which will give you a nice light opening, the sides can then be painted a light colour. The hearth I would recommend something rustic such as an Indian stone which will tie in nicely with the oyster back. If you square off the opening this leaves you the option to install a beam or not. I have attached a picture of something like what I would recommend. The stove is a DG Ivar which at the minute is an extremely popular option.

Nice! Why don't you do the brick on both sides? Only on the bump out parts?

I don’t think the brass is the issue tbh. I’m not sure the surround colour works that well with the back piece of the fire nor too well with the wall. Do you have something red/pink in the room that is reflecting on the left hand side of the pic as it looks much pinker in that corner? What colour is the sofa and what’s the actual wall paint colour?

Yes an oak top and painting the tiles sounds like a good solution if you just want it to look better / more in keeping with the rest of the room and you don't plan to use the fire. If you want to be able to use the fire then make sure whatever paint you use and mantlepiece top you install will be compatible with the heat from the fire and not combustible. As an alternative you could also tile over the top of it with something more modern looking but this would take a bit more skill and more cost - it would change the texture of it though and keep it fireproof (as long as the tiles you use are sufficiently heat resistant and suitable).