Just cleaned a gutter today, I was told roofers had done a "chemical clean" before the summer. Front West facing has moss all along the bottom of the tiles and clumps here and there with some green growth visible. Side North West facing has less moss but still loads and algae is visible. The North East facing rear has moss and algae growing with clumps of semi dead moss stuck to the tiles.
Two or three of them could have removed the moss in two hours (including two tea breaks) and then applied the chems. Instead it looks crap and needs more chems to kill off the remaining moss and algae.