Are you wanting a nn from just the middle name, because I love [name]Helen[/name], nn [name]Lena[/name] or [name]Ellie[/name].
[name]Helen[/name] [name]Scarlett[/name] nn [name]Arlie[/name], [name]Lettie[/name], [name]Carlie[/name] (but this is probably too close to [name]Charlie[/name]), [name]Arlo[/name], [name]Carlo[/name]
[name]Helen[/name] [name]Judith[/name] nn [name]Judy[/name], Dittie
[name]Helen[/name] [name]Avalon[/name] nn [name]Ava[/name], [name]Avie[/name], [name]Lonnie[/name], [name]Lona[/name]
[name]Helen[/name] [name]Beatrice[/name] nn [name]Bea[/name], [name]Tricia[/name]
[name]Helen[/name] [name]Eleanor[/name] nn [name]Ellie[/name], [name]Ella[/name], [name]Elsa[/name], [name]Annie[/name], [name]Anna[/name], [name]Nora[/name]
[name]Helen[/name] [name]Evangeline[/name] nn [name]Evie[/name], [name]Vanna[/name], [name]Angie[/name], [name]Ellie[/name], [name]Linnie[/name], [name]Lina[/name]
[name]Helen[/name] [name]Felicity[/name] nn Fel, Fellie, Lica, [name]Lisa[/name], City, Citta, Ittie
[name]Helen[/name] [name]Frances[/name] nn [name]Francie[/name], [name]Frannie[/name], [name]Fanny[/name], [name]Annie[/name], Ancie
[name]Helen[/name] [name]Imogene[/name] nn Immie, [name]Imo[/name], Oggie, [name]Genie[/name], [name]Gena[/name]
[name]Helen[/name] [name]Juliet[/name] nn [name]Julie[/name], [name]Jules[/name], Liet, [name]Lia[/name]
[name]Helen[/name] [name]Margaret[/name] nn [name]Maggie[/name], [name]Peggy[/name], Garet, [name]Meg[/name], [name]Maisie[/name], [name]Megan[/name], [name]Meggie[/name], [name]Margie[/name], [name]Margo[/name], [name]Rita[/name], [name]Pearl[/name] ([name]Margaret[/name] means [name]Pearl[/name])
[name]Helen[/name] [name]Penelope[/name] nn [name]Penny[/name], [name]Poppy[/name], [name]Pippa[/name], [name]Nellie[/name], [name]Ellie[/name], [name]Lola[/name], [name]Lollie[/name]
[name]Helen[/name] [name]Tabitha[/name] nn [name]Tabbie[/name], Tabbit, Bittie, Ittie, Bitha, Bith, Bit, Tabs
[name]Helen[/name] [name]Winslowe[/name] nn [name]Winnie[/name], Innie, [name]Lola[/name]
Good luck and I hope this helps! (I love the nn [name]Ellie[/name], can you tell?)