I think you'll find that one year down the road you will get a nasty renewal surprise. That seems to be completely normal for pet insurance. We went with Argos (yes, the catalogue shop) and got a good deal for the first year. We had to make a claim (which wa said without fuss or added exclusions) then got a renewal for a couple of quid more than the first year. I was expecting this but it wasn't too bad.
However, in between policies they changed the underwriter and you can expect to see that happen with any company that isn't the underwriter the,selves, such as Asda, John Lewis, Directline etc.
We recently made another claim for over £1,000 and it was again paid without any quibbling or delays and they haven't added any extra conditions as a result. So far I can't complain about them, and I know that changing companies will result in higher premiums because Posie has now been treated for something.
I think most companies are the same, at the end of the day, with the possible exception of Petplan. They quote much higher figures from the start but then don't increase premiums by so much at renewal.