Had been with Argos for 7 years with lifetime dog insurance for my CKC, never had any complaints as they always paid out promptly and had good customer service, unfortunately the premiums started rising over the last few years (even though I had not made any claims for years), and it became unaffordable. Looked around on the internet and compared policies and prices for lifetime with many different insurers, decided to go with this company for a few reasons, affordable monthly premium, good level of cover and if he has shown no signs of his previous health problems for a few years he will be covered. Slight downside is the £95 excess and 20% I will have to pay if any claims made due to dogs age, but I guess this is how premiums are kept reasonable, hopefully they won't rise massively like they did with Argos every year.
So far so good, obviously you don't know how good customer service/claim dealings will be until you make a claim, and there are no reviews with regards to dealing with claims, so will have to wait and see.