The Lee Valley White Water Centre, located in Hertfordshire, will host the Canoe Slalom competition during the London 2012 Olympic Games. It just opened to the public. (i think this is only good for those aged 14 and older)
what the site says:
riding the rapids before the world’s best athletes! We’re open from now until the end of September 2011 – now’s your chance to enjoy adrenalin pumping white water rafting, canoeing or kayaking at the newest and best white water venue of its type!