I'm with you on the PetPlan insurance! We have two rabbits, both rescue buns aged one and two years.
The bunny who is two is insured with PetPlan at a cost of around £17 a month which is a lot for his age. We've made one small claim when the bunny had stasis after coming home from boarding accommodation (not the boarders fault whatsoever, just one of those things). Due to the high cost of insurance, we haven't got the other rabbit (one year old) insured yet.
We previously had two rabbits. One was nearly 13 when he died 18 months ago. He'd never been insured and actually, apart from a minor esr infection as a baby and mild stasis a couple of times in his life, he was never ill. Barely cost me anything, that lad! The other bunny died last year at 9 years old. I'd got her insured when she was a baby and my GOD PetPlan must have hated me! She had so many illnesses and at one point had surgery so major for a mandibular abscess that she was on antibiotics for the rest of her life (about 4-5 years). PetPlan, to be fair, ALWAYS paid out on our claims for her - probably tens of thousands of pounds over the years. When she was a baby (ten years ago now), the insurance cost less than £5 per month. By the time she died I was paying around £22 a month and she was considered old by that point!
Put that I'm contrast with the £17 per month we pay now for our 2 year old rabbit. The mind boggles!
Interestingly, when we had a dog (passed away 3 years ago now at nearly 16), I looked into insurance for him when he was about 10. They wanted just under £350 per month for him which was about the same as my (then) mortgage. I passed on that one but instead saved what I could each month and had a separate vets bills bank account.