Sphaerobolus stellatus -- has very many 'English names', Cannonball, Artillery fungus, Shooting Star.
It is very common although this is the first time I have spotted this 2mm diameter species. It is a Gasteromycete (puffball/stinkhorns etc). It is said to grow on rotten wood, decaying herbaceous stems/grasses and also dung. This was on a cow-pat in a 'cattle-compound' at Pembrey saltings.
The 'sphere' containig spores is shot out 20ft horizontally and 14ft vertically. It seems there is a build up of osmotic pressure from various sugars giving energy to propel the spore-mass.
It is responsible for 'patches' of golf-links and the spore mass has been blamed for dirty spots in rooms/wallpaper when the fungus grows in plant pots.