I had to clean out the guttering, so while I was making a rare trip up a ladder to check the roof, I thought I'd also check out the ecology of this so far unexplored place.  I hadn't really tried to sort out the garden's mosses and lichens yet either, but the roof tiles are definitely the best place to go looking for them.  There was quite an impressive collection of yellow and grey ones, all seemingly doing okay despite us hardly having had any rain for several weeks.  Probably I'll need to go up again, but some of the species I did find included the yellow/orange Caloplaca aurantia (#274), flakey grey/green Physcia caesia (#275) and Aspicilia contorta (#276) with its grey/white circular pock-marks.  Also plenty of Redshank Moss (#274); the main reason I needed to clean out the gutter in the first place.