The only regs i know of are distance from the ground min 350mm to the bottom of the indicator , max 1500mm to the top , max from the edge of vehicle 400mm , minimum speration 500mm ,
All the above measurement are from here http://westfield-world.com/svalights_front.html
But i would add that the main reason for indicators are to show other road users what you intend to do , the more your intentions can be seen the less there excuse can be for saying didnt see you mate sorry for your broken nose !!
Think self preservation and keep smilling .
Mike