I have just removed my old 1970's brick fireplace, and would now like to fit some sort of insert into the hole. The plan is to just have a nice clean neat hole where my wife want's to put some candles. I have had a search on the internet for 'fireplace insert' but I cant seem to find just the insert on it's own.Is there another name for what I am looking for?
Don't think there is such a thing. Probably needs lining out with foil backed plasterboard or water resistant MDF on Softwood battens. Remember to leave some ventilation into the old flue to prevent damp problems.
What about digging out the old fireback and as much masonry as you need, and plastering it all around including the back of the recess. You could let in a nice thick piece of slate a few inches above the floor just like a window sill. Notch the sill around the front wall face in the same way a window opening would be treated.
You might be able to find a plaster niche from an upmarket supplier (although I haven''t found one on the net from a cursory surf), but likely to be expensive and probably difficult to get one that fits "off the shelf".
Construct your own, as already suggested, seems the best idea