This moth fits exactly to Skinner Vol.3 plate 45, no.7.
It has the off white underwing and the upper wing markings are same. According to Skinner there have been 5 British recs to 2005, but I imagine there may be more. At present it is only a provisional ID.
Amazingly this moth was in the trap Sunday but it flew off before I could pot it, it landed back on the trap at c10.15 tonight - what luck.