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.

Just to repeat what a couple of others have said. The cabinet is in great condition and a good colour. perhaps change the knobs for a very simple small aged brass or even a dark bronze button type. Change the lamp as it is too big for the unit, the shade is pressing against the wall, (it could work well on a side table by a sofa perhaps). Exchange it for a lamp with some brass incorporated into it (very popular and in most decor stores now) and it could look lovely. the difference between painting or leaving the unit, depends on the final look you are going for. If you want a more classic feel. Don't Paint, go with the above suggestion. If you want more quirky as some of your accessories suggest, Then Paint and adorn with crazy abandon! Happy days!

I'd be temped to paint it white and either put a black cast iron insert in or line out the opening with brick (love the herringbone example shown below) and put a wood burner in. http://www.chesneys.co.uk/products/accessories/interior-panels/ches-brickherin

Aw shucks guys! Thanks! I’m definitely aiming for a tiny bit more stylish. My partner brought that heinous green drainer from his house and was everso pleased with himself for solving a problem I wasn’t aware I had! And the el cheapo Wilko kettle is a placeholder til I get a boiling water tap, so I haven’t upgraded it for three years. Plus he’s got a brewing corner in the kitchen, and a 3D printing bench in the utility. I’m just glad to have his wallpapering skills! Though we had a difficult conversation when he replaced my Henry who fitted under the stairs for his Dyson which doesn’t :-)