Personally I haven't taken out insurance for Merlin because I can get hands on the money if needed. I get fed up putting money into a black hole and finding (the few times I have ever made a claim) that there is always some reason you're not covered...
My Dad had insurance for his Working Border Collie, who managed to rupture a disc in his neck. We ended up taking him to see Colin the Neuro Specialist / Surgeon up at Fitzpatrick Referral's, aka The Supervet, for an MRI scan, then emergency spine surgery to repair the disc. It had leaked and compressed the spinal column by over 60%, and they had to remove the leaked gooey stuff, then repair the hole and reinforce the vertebrae to avoid a repeat.
Dad had taken out insurance through the vet, and when it came down to it, they only covered the very basics - Boosters, Worming, etc. Despite the plan having been £30 plus per month, they had a 'hidden' accidental injury clause where if it had what they deemed as 'natural causes' then it wasn't covered. Bobby, thankfully, is absolutely fine now.
The bill was well into the thousands, and they wouldn't even consider paying for the scan, the meds or rehab.... No chance ref the surgery itself... I now kind of own Bobby's left eyeball, and right elbow......
The practice is absolutely how you see it on telly - although even more impressive when you get there! The staff are so nice, and you feel secure that they will move Heaven and Earth for your furbaby (etc), if they have to. Noel and the team are Superstars!