take video evidence of the balloons flying near or over your land and of the ponies/horses/livestock panic stricken, im sure there must be laws with the aviation authoritys that they are supposed to be adhereing to, log a complaint with the police everytime they fly over the land, keep a diary listing dates and times, contact with police, phone calls to the company, written replys from the company. if you build up enough evidence you may be able to take them to court,
get your solicitor to write to them, that alone might be enough to dissuade them from flying over your land and may be the