Tried the aspen copse in the birch wood at Pilmoor again for a couple of hours last night. No more Lead-coloured Drabs, but just before I packed up I spotted a micro on the sheet that resembled Semioscopis steinkellneriana, but I remembered there was another that looked similar. I potted it, and sure enough it was the ' other one' a Semioscopis avellanella. Checked the record with Charlie Fletcher who kindly supplied the Yorkshire distribution map for this species.
On the way home, had a Barn Owl quartering the verge close to Pilmoor and another nearby at Thornton Bridge - always great value to see.