Coal quality is strongly correlated with depth - easily-mined surface coal is invariably of poorer quality than more costly deep-seam coal. The economic viability of coal power generation is largely contingent on the use of the cheapest, most easily extracted coal. Britain has enormous coal reserves, but those reserves are nearly all deep and hard to reach. We import huge quantities of brown coal from Germany and Eastern Europe, because it's around half the cost per unit of energy, even after transport costs.

Australia is an edge case, because of the huge reserves of coal relative to a tiny population.