Red Twin-spot Carpet.
(Xanthorhoe spadicearia)

Unfortunately this is a somewhat faded specimen and it was quite difficult for me to identify.

Information:
Fore-wing length: 12-13mm and flying April-August fom dusk onwards or if disturbed whilst roosting in bushes during the daytime. They can be found in most non-city environments throughout mainland Britain. The shape of the two bars enfolding the dark, wide central band is typical as is the cross-line near to the head. The other diagnostic pointer is the pair of dark, often red, spots near to the wing tip and about a quarter of the way in.