SEIB, costs about £58/month for an R reg mercedes 3 horse, includes highest level of breakdown & recovery of horses back home, etc, have been with them for years, can't fault them
Antony D Evans and have the breakdown cover as well . It has been brilliant the twice I used it , once for a puncture and once when the fanbelt snapped, even though Claire had unloaded and hacked the last 4 miles to the show they offered to arrange a horsebox to go and pick her up and take her home as it was a Sunday and they had to recover the lorry instead of mending it. It wasn't necessary as we had found a good samritian already at the show.
Anthony D Evans for insurance & breakdown cover. Called them out once for a minor problem. They attended very quickly & sorted the problem. can't remember the premium but it was reasonable.