I took a deep breath and let a colourist I trusted (Sophie, at Valentino, in Thackeray STreet in Kensington, 020 7937 6911) do what she wanted, which was to paint in various tones more closely related to the natural colours of my hair than the bleachy blonde bits I'd had before. It was a bit of a surprise (being that bit less bright) but it's working for me, and it also means I don't get obvious dark rooty bits within a few weeks