I have to agree with Rebecca, i've been using home dying kits for approx 10 years now and this is the best one I have found.

Without a doubt the best home highlighting kit is L'Oreal's Couleur Experte, £9.64 from Boots. This two-step kit uses an all-over base colour followed by a simple highlighting technique using a highlighting precision brush that allows you to pick out the sections you'd like to enhance with a toning shade of dye.