Mark Woolley, of Electric Hairdressing, a L'Oréal colour specialist, offers a word of caution. "The trend this summer is for much lighter hair but unlike last year's LA beach bleached look, 2011 is all about sleek blonde hair. If you overcook it, and I think Cheryl has, you will end up with unnatural, dry, damaged hair. Take a page out of Katy Perry's book and do it gradually. And never use bleach."