Having failed so far to get a new stove for my room I am tending to spend most of my time in the kitchen which has a working wood burner and stays relatively hospitable even when its minus something outside. Still there have been some gloriously sunny days of late.
Answer, it’s part of the wood stove, a kind of ceramic or brick lining for the air outflow at the back of the fire. Apparently the company that made the fire ceased production of the “Eco” model 15 or so years ago and stopped producing spare parts such as this a couple of years later. Lets hope the replacement bits – that cost me 40euros – will last at least another 15 years.