Looks like a bluebell, except that it is white. Not Lily of the Valley. (There were also a few bluebells in flower nearby.)
No interactions present.
Three Cornered Leek (after the three-cornered flower stalk of this species). The NI 'Habitas' website for the flora of Northern Ireland does show records for Allium triquetrum in this (North Down) general area. There are a few NI records for Allium paradoxum but described as 'very rare' and 'at a small number of shady sites'.
Lat/Lng: 54.663, -5.787
OS grid ref: NW558363