I have my horse insured through petplan (not sure if thats ok to say? Mods remove if not)
Touch wood I have never had to use it, so can't say what they are like to deal with ( except that they are very efficient at taking money from my account!)
I pay about $35 per month. For this I am covered for vets bills, with an excess of $1000 (so you would only claim if over $1000) I figured I could probably cover $1000 of bills, I would need help for super expensive bills. You can get an excess of $350 (i think it is) but that was going to cost significantly more. I would also be covered for all costs if she needed to be pts, and some cover for tack in case of theft, the amount of which escapes me.
If you look at the petplan website you can choose what you would like to be covered for and get an automatic quote at the end.