Petplan have paid out over £25k for our 10 year old lab over the years (4 major ops plus ongoing medication). They are very easy to deal with, though not the cheapest.
As others have said, the life cover option (whatever it’s called, covers an injury/disease that the pet has had in one year, in future years) has been good for us.
We also found that our local vet hospital will only deal with certain insurance companies (so if your pet had an op you would have to pay up-front then try to claim back). A cruciate ligament op can be more than 7k!
Our local vet claims for medication (glucosamine and anti-inflammatories) from Petplan direct so I don’t even have to pay up-front for that.
MrsT