Creating a nice alcove in old fireplace

[1000Stars]

Hi
I'd be grateful for any advice. New house so I'm slowly getting around to decorating it. Pulled out the electric fire from within the chimney breast and this is what was behind it. Obviously it's ugly, how can I turn it into a nice alcove like the other picture-not exactly like that but just with a similar smooth finish so I can pop some candles in there or other random crap! Where do I start and who do I even get in touch with to make it happen.
Thanks

[HipsterHunter]

Basically something has to go up above to stop crap falling down like a chimney balloon, then the fire place needs to be plastered and painted. Keeping some ventilation for the chimney is important.