The amethyst deceiver (Laccaria amethystea) is is a lovely, delicate fungus of shaded woods where it can be quite abundant. It occurs elsewhere but shaded woods, both deciduous and coniferous, are the most likely place to find it. It is especially associated with beech trees.
It occurs from late summer right through in to winter but September and October is most likely. It is most easily distinguished by its unique colouring and it is probably the only mauve (or lilac) fungus to be found in the United Kingdom.
It is edible but has very little taste or smell so it is probably best left alone to delight others who may pass by later!