I'm a Charlotte and really like my name. I have met quite a few of them but it's not really been a problem - particularly when a few of them go by Lottie or Charlie (which I don't). I like that it's easy to spell and pronounce and is feminine without being girly.
Helena is one of my favourite names - definitely my favourite from your list!
Other names you might like are:
Adeline, Alice, Arabella, Augusta
Beatrice
Camilla, Caroline, Christabel, Colette, Cora, Clara
Edith, Eleanor, Eliza, Elizabeth
Florence, Frances
Gabrielle
Harriet, Hazel, Hope
Iris, Isadora
Juliet
Louisa, Lydia
Mabel, Mirabelle, Miriam
Pearl, Phoebe
Ruth
Seraphina
Violet
As you've got a Daniel, you might like to consider some other Biblical names. Personally, I really like Rebecca. Esther, Joanna, Leah, Lydia, Martha, Miriam, Naomi, Rachel, Rebecca/Rebekah, Ruth, Tabitha, Phoebe, Susanna, Hannah?
I don't mind Alison either, to be honest, but I prefer Alice. I don't really like the nickname Ali/Ally either.