Am at my wits end with my 3 year old....she has always had a temper but seems to be getting worse. She used to bang her head (off floors, walls etc) when she was 2 and I thought she'd grown out of it but has recently started again. She shouts and strangers, is totally uncooperative and gets herself into suge a rage that it can take a while to calm her down. Tried reward stickers/charts and lots of praise when she is well behaved. When she is good she is a complete angel but more often than not she is a terror !!

It sounds to me like your daughter does not like to be controlled. She will be a leader. Strong personality.
I would suggest to do some reading about how to connect with a child like this. She thinks everything should go her way or something like this.

I have still not found a better book for communication with children than, Raising Our Children, Raising Ourselves. It not only shows you how to understand the reasons behind behaviors and how to cure the cause, but helps you deal with the part of yourself that prevents you from being kind in tough time.