White flowers variously marked with green, similar to other snowdrops; there are hybrids and cultivated varieites with slightly different markings.  Greyish-green leaves, wider than the common snowdrop, with hooded tips.  The base of the outer leaf is wrapped around the inner leaf; in other snowdrops the two leaves are side by side at the base. 

The BSBI has a key to common UK snowdrops here: https://bsbi.org/wp-content/uploads/dlm_uploads/Snowdrop_identification.pdf (M J Crawley, 2010)

other Galanthus

Photographs should show basal arrangement of leaves

gardens, parks, roadside verges, churchyards

early Spring

commonly planted in gardens, etc., and may survive in the wild as a garden throw-out

see the BSBI guide to snowdrops http://bsbi.org.uk/Snowdrop_identification.pdf