I'd favour Confused, but the resolution is a bit soft, so not 100% sure sorry
Plus those particular stigma are a bit weird for Confused?
An odd looking thing. A bit late in the day now, but I don't suppose you kept it?
Have you ruled out a late dark version of Acronicta aceris?
I does feel more like an Acronicta than a Apamea, but I was not aware of a dark form of Sycamore (A. aceris).
Stephen has sent me some other images and I'm happier that it is at least an Apamea now - the markings along the termen match. As to which, I think Confused is the more likely of the two, albeit a slightly odd one.
Many thanks for taking the time to clarify Dave, it's most appreciated.