Holly, have you tried a ceramic straightener?
or permananetly (spelled wrong again...sorry) straightening your hair, my mom does it often, and she can still curl her hair and stuff when she needs to like on special occasions and such.
I really recommend the ceramic straightener though, my friend Jessica who is black, has very thick, dark, curly hair, I mean thick. she used the same straightener I did, and it was silky straight and her hair was actually shoulder length when afterwards.
Manda