I can assure you that if you fitted a solid fuel appliance in that fireplace it would not be to building regulations.
I fit stoves for a living, a chimney fire with a closed appliance below can reach temperatures in excess of 1000 degrees, enough to damage brickwork, imagine your in bed asleep you have a chimney fire, enough heat is generated for the stove to glow red hot, fumes are now leaking into your bedroom and your wooden surround is on fire from radiation from the stove.
A cursary glance at document j of the building is not really good enough for something that could put you and your family at unnecessary risk.