I live in a flat in an old nineteenth-century building. We have an open fireplace, but no fire. We investigated installing a fireplace, but the flue/chimney is damaged, so we want to get the fireback (which is crumbling) repaired, and we want to block off the chimney to stop debris falling down: as quite large pieces of mortar come down, we don't think a chimney balloon would suffice. Which category should we post the job under to get the right specialist?