To a balayaged dark blonde:
Firstly, I had to bleach my hair. I did this twice, using the Jerome Russell B Blonde High Lift Bleach Powder. This is for use on dark to medium hair and I got it in Boots or Superdrug. (Linked). Worth nothing that when you buy this, you also need to buy the lotion to go with it. (I used volume 30 but for stubborn hair maybe try the 40.) I mixed it up in a ceramic bowl and bought this tinting brush from Superdrug as well, and then applied it using the technique illustrated in this Youtube video. My boyfriend kindly did the backs for me!
I bleached my hair twice in two days, leaving the bleach in for 45 minutes each time. The end result was a yellow/orange mix which I knew would happen. Your hair will always go orange if you are bleaching it and it has been dyed previously. It's unavoidable. I left my hair for 24 hours to rest, before adding the toner. The only way to get the orange and warm tones out of bleached hair is to use a toner or purple tinted dye. Any hair dye with the words 'cool' or 'ash' in the name will be purple tinted. To take my hair from the picture on the left to the picture on the right below, I used a permanent Clairol Nice 'n' Easy dye in the shade Natural Dark Cool Blonde #7 (formally 106D). As you can see below this eradicated any warm tones.