I use Animal Friends for my youngster. I did a price comparison and they came out best.
Ditto for both of mine, and the cats. Only had to claim for one of the cats though, never the ponies, but it was straightforward and worthwhile, got 100% back (minus excess obviously, but that was pretty low). My trailer is also insured through Animal Friends, I'm fairly sure it works out at £40 altogether for 2 ponies, a single trailer and two cats!