Thanks PaulR, I have Birmingham to my North, although Sunday's shot was more north-west.
I've been frustrated looking for NLCs over recent years, never been sure exactly where to look and at what time and haven't knowingly seen them before this year. This year's displays have been so obvious although the timing's still quite critical, and of course variable depending on altitude and date. I first looked just afer 22:30 and they were brilliant, reaching almost up to the zenith. By the time I'd grabbed the camera and fired off some shots they were perhaps past their best although the photo still only shows a small part of the total display and doesn't really do it justice.