I am not knowledeable enough to say whether this is N. sparsella. This specimen seems to have a black head. whereas many of this species,although not all, I can see online have a white/yellow head. Again I don't know whether head colour is diagnostic,
Yes, the head colour of N. sparsella does appear to be yellow. Rosenstock, in describing the synonym Adela chrysolamprella, mentions ochreous hairs on the head. The only other Nemophora occuring in this area appears to be Nemophora laurella, so I have suggested that.
Yes. given this specimen has mainly a black head, I'm happier with N. laurella. I'll add that species to the taxonomy -assuming CNM will accept it OK. Although I note this specimen also has a distinctive yellow thorax, which I think looks different again to the ALA examples of N. laurella. So I think I will stick with an ID of Nemophora (genus) in this case for now. However I wonder given the iridescence, whether how the light falls on these species has a very big influence on how they look.