If you want to take Gatorade powder you can order online at http://www.gatoradestore.co.uk/products/perform-powder-lemon-tub
Or I believe Waitrose stock SiS powder
If you want to take Gatorade powder you can order online at http://www.gatoradestore.co.uk/products/perform-powder-lemon-tub
Or I believe Waitrose stock SiS powder