It's difficult to make comparisons because even your home postcode can make a difference to premiums, as well as breed, age and sex of dog and the type of cover.
I'm with NFU and have lifetime cover for both dogs. I pay £33 per month for 7 year old Louis and £73 per month for 12 year old William. Louis' excess is £55 for each new claim and William's has gone up to their max. which is £200 for each new claim. I don't have to pay a percentage of the bill on top of the excess. NFU don't impose that as far as I know.
I've claimed loads for William over the years. Certainly since he was about 7 or 8 I've claimed more than I've paid every year and even before then there was a year when I claimed just under £2,000 for a MRI scan, other diagnostics and physio etc. when his back problem started and was eventually diagnosed as lumbosacral disc damage.
Every year I claim around £200 for William's 6 monthly ophthalmic check ups and Optimmune ointment for Dry Eye and around £240 for the acupuncture that helps so much with his back. They are ongoing conditions so I don't pay any excess on them, having paid it once when the initial diagnoses were made. This year I've also put in a claim for over £500 and another for £650 for the two lots of surgery he had in May and June.