18 years old gas fire by Living Flame Limited of Plymouth (no longer trading). Tray is filled by a 50mm thick blanket of a white, mineral fibre-like material (looks like layers of cotton wool). Upper surface upon which ceramic logs and the coals sit, has hardened over time and gas is not all permeating through, pushing some out of the sides of the tray and sooting the fireback and sides (incomplete combustion). Tried all known local sources and no-one can identify the white 50mm blanket material. Appreciate any help.