Female Banded Demoiselle - or is it?

I learned recently about a colony of Beautiful Demoiselles (Calopteryx virgo) at Ferry Meadows, Peterborough. This species' usual range is well away from here so went for a look on 29 June. I only saw Banded Demoiselles (C. splendens) for certain but this female was very obliging and appeared to have very dusky wings. Several people have commented that it looks fine for C. virgo but I think I will wait to see a male.