A few weeks ago my hair underwent a rather large change! It involved a friend losing 11 hours of her life bleaching my hair more than should ever be allowed, and many many pots of dye. But I am so so pleased with the outcome, I feel like a My Little Pony, especially when I consider my thigh tattoo.
For reference, I used (several lots of) Jerome Russel B Blonde cream peroxide and powder bleach (for medium to dark brown hair) and a combination of La Riche Directions hair dye in Violet and Lilac, and Smart Beauty hair colour in Electric Blue.
I top up the colour once or twice a week before I wash my hair, and I've just topped up my dye range using this ebay seller, where I got five pots of dye, as well as postage, for £19. In my regular shop, they cost £4.50 each! Five pots of dye is going to last me at least 2 months, probably more!
I have also been using Touch of Silver Brightening Treatment as my regular shampoo, as this leaves a lilac tint on blonde hair if used too often! There is logic there.