If I may, ladies...
I see your lush caca and raise you a BAQ henna application.
Body art quality henna from Pakistan or Yemen or Egypt etc, (the stuff used for mehendi) is pure, finely sifted henna powder. Nothing added. (Lush add some other bits and bobs, I believe)
Add water, mix into muddy gloop, wait for dye to release, stick on head, wait an hour or two or longer, wash off.
Completely permanent, natural copper / red.
Test it out on some strands from your hairbrush before you put it on your head in case you don't like the colour. Because it's bomb proof once its in your hair.
And how I didn't find this sooner after years of trying to give my red bonce a bit more vavavoom with salon dye I don't know. My hair is reverting to the glossy silkiness of my youth. Amazing.
there's a very informative website called www.hennaforhair.com which has a lot of pictures and research, but there are UK websites selling the stuff. I got mine on ebay, a brand called Jamila.