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.

There is a little show at the Cherry Tree village (just south of Southgate) that has a lot of this type of fireplace for sale. My daughter bought one which was initially rusty and the shop made it beautiful. They also offered her a good choice of tile to go in the sides.

Hi, into only taken 2 years ..but finally finished the room, the box to the right of the fireplace we found out housed gas pipes so ripped all that out, couldn't put in a wooden 1930's fireplace if I wanted a burner due to fire regulations, so opted for a concrete wooden effect beam, with a natural slate underneath , we stripped the walls, replastered and finally painted... just waiting on my new curtains and I can shop for a nice new rug possibly :) before and after ...

If you do put your TV on a long low console where the fireplace now is, you will most probably have space for a chair in the corner where the TV now is. You could put the floor lamp that is now next to the smaller sofa with that chair, or at least in that corner. Then put lamp that doesn't take up that much space in the corner with the smaller sofa. I hope you'll have enough space left for a coffee table of some sort. Do you know the dimensions of your room? I would have loved to put the coffee table in the right direction, but can only do so much photoshop magic ;-)