I approached a couple of insucrance companies here in the UK. Pet Business Insurance and Cliverton are the most popular. For our not for profit training club I went with Cliverton as they are very experienced in this area and provide Professional Indemnity, employer (for volunteers) insurance and public liability. They also cover for any absence from work due to injury from a dog for instructors.. We are covered for a number of events each year in addition to regular classes.
For the new venture I had need for insurance for home-made dog treats which is not available through many insurance companies here so I went with Petplan and it provides all the cover above plus our own home-made dog treats and pet-sitting.
Each company took all my details and came back with a range of options to ensure I had the right cover. None of them have been expensive all are in the £250 – £350 ballpark.