I agree with Man About the House. If you can create a structure to cover up the whole of the fireplace, not only would this provide a centralised focal point, but it would also conceal the rather dated fire surround, giving you a blank canvas to then do what you want. Let us know how you get on. Kate www.TheHomeDesignSchool.com

Regarding the fireplace, what type of fire are you thinking of having? If its a real wood fire of gas fire, then you may need to take into account a chimney/flue system. It looks like both options you have suggested have the fireplace in the original house and not in the planned extension, which means any flue/chimney would likely need to to run up through the house and may cause issues with the space above. There are some great options available when it comes to fires and stoves that might allow you to position the stove away from the wall and perhaps more central in the room. Double sided stoves with glass on opposite sides are good options when you have bi-folding doors as you can enjoy the ambience of the fire from both inside or outside.

I don't think the wooden surround is original to the tiles (though both could be unoriginal to the house) The black one would look good with a nice metallic paint like bronze and ditching the wood beading round the edge. Or kept in a matt black and dry brushed with a metallic paint to pick out the detail The tile one needs either a) completely removing if you don't like it b) painting the surround and maybe adding a little touch of 1/4 round beading to try and harmonise it with the tiles c) a new surround to match the tiles.

I think your fireplace looks lovely as it is. Adding a piece of oak makes it look a tad heavy?