We've just removed this from our house following some building work. The actual fireplace insert is in two pieces - appears to be cast iron as far as I can tell. Age unknown - I've checked the back and there's nothing I can see to identify it. Good condition. It's not been used as a fire for at least 10 years as the chimney was capped. The main metal insert is 91.5cm (H) x 76cm (W).
The surround is comprised of three stone-like bits (don't know what they are actually made of) and a wooden top shelf (131cm width).
Sorry I don't know much about this and I'm far from a fireplace expert!
Collection in person only from Ripon, North Yorkshire.