Ordered a Camelbak Flashflo from cyclexpress.co.uk for £25 with free delivery. Tried it out this morning and it's ace! If you squeeze the excess air out before closing it, the water jumps about less. It's really secure and the tube is really easy to use and clip into the belt. Would definitely recommend getting one. My bottle belt is going straight in the bin! Thanks to GaryT and others who convinced me to order one.