We were with Petplan. We paid in for years without needing to claim, and then as our cat neared end of life it needed a couple of big ops that came to about £3000 and more than repaid everything we'd paid in, and Petplan paid up no problem.
So, care can be expensive. Your choices are to set some money aside each month to pay future pet bills, take out a loan if and when you need it, buy insurance or be prepared to put your cat down if you can't afford to pay for its care.