What do you need in your festival "survival" kit?

Maybe Electrolytes? (for rehydration) You'll find them at Boots; powder sachets you can add to drink when you get dehydrated (either from too much sun/too much drink!) Also maybe Carex gel or Cuticura - gel you rub into your hands if you can't get to anywhere to wash them! (You'll also find that in Boots, with all the soaps/handwashes)