A few websites that might be of interest:
Intelligent Horsemanship Association : http://www.kellymarks.co.uk/
Intelligent Horsemanship Kids : http://www.intelligenthorsemanship.co.uk/content/view/52/102/
Informed Bitting http://www.informedbitting.co.uk/
Project Horses: http://www.projecthorses.co.uk/
Natural Horse Supplies: http://www.naturalhorsesupplies.co.uk/