In English, HEL in a; in Afrikaans, heh LEEuh nah, with nn LEEuh nah.
I prefer
Helen, and I've never known one with any nn,
Nellie,
Hel or anything else. I do know a church minister who chose to name his youngest daughter
Eleanor rather than
Helen because he was sure his other children would have shortened it to
Hel, which he was naturally uncomfortable about!