Pale-shouldered
Brocade.
(Lacanobia thalassina)

From a few feet away, almost invisible against the woodwork.

Information:
The thing to look out for is the 'pale shoulder' - that light patch where the wing joins the body ... closest to the head. There is a broad band across the fore-wing, edged with a pattern of inward curving creamy arches. Nearer to the trailing edge there is a zig-zagged line of the same creamy light colouring in which there is a 'W' element.
They fly May-July in most of Britain in wooded areas, fens, gardens and moorland - but not in an urban environment. The fore-wing length is 16-20mm.