I've been using Bumble and Bumble's thickening spray on and off for years, and now they've launched a whole host of complimentary products. My hair is thick anyway, but the Bumble and Bumble Go Big Thickening Treatment (£24) really helps to keep volume in my roots, without making my hair feel sticky. For finer hair types, just use it all the way down to your ends! — Gemma Cartwright, senior editor