Lichens are composite organisms: a fungus and a plant working together, often to grow in a spot where it seems the only source of nutrition is the air. Many lichens produce structures rising proud of their main growth to disperse the spores or diaspores through which they reproduce. The ones rising here are towering and trumpet-shaped, indicating the lichen is possibly Cladonia fimbriata, a species often found on the tops of walls.
This one was growing on the top of the wall of Compton Hospice. It is growing surrounded by moss which is also sending up its fruiting bodies. They look like tiny elongated bladders on the end of long, thin stalks.