Most of us think that these are ancient monuments or stone age creations, but I believe that most of these horses and other things carved into the lime stone hills are just 'follies' By this I mean they are pieces of art produced specially to provoke the reaction that they get. Most were made less than 200 years ago.
One of the most famous and potographed is the Cerne Giant. It is only a few miles from where I live. It is supposed to be thousands of years old and an ancient fertility symbol, but it turns out that again, it was made only a couple of hundred years ago. There are no records of the giant in a monestary which had been on the site for hundreds of years.
photo below, (what a naughty giant!!)