Do not get sucked in by initial low policy costs. I do unfortunately have 3 pets still insured with Sainsburys, all having pre-existing conditions so I cannot afford to switch insurers and have pre-existing conditions excluded. My almost 14yr old Greyhound's renewal has just arrived (it is his premium increases that are my issues with Sainsburys) and it has increased from £220 to £300 a month - YES a month - not a year!! Originally his premiums started at £16 a month when I got him in 2005. Sainsbury's have paid out on most claims without too much hassle although a couple of times they have tried to say that it was part of the same condition and so they had already paid the max £7,500 out. Once specialists are involved it doesn't take long to reach bills that run into thousands. In December we had a cat cost almost £4,000 in specialist and normal vets bills (the first ever claim for her) they did payout without any issues, her renewal is due in July - it will be interesting to see what that will be. Although all the cat's premiums have doubled since I first insured them in 2006. My 4 other animals are insured with PetPlan whom I haven't had much experience of claims or the subsequent premium increases, but I have friends who have and they say their premiums have never increased as dramatically as mine have with Sainsburys.
I like to insure my animals to have peace of mind but it doesn't help when insurance companies take the pi$$ and increase the premiums to ridiculous amounts but until you make a few claims you never actually know how good insurance companies are and by then its too late if you've chosen a cr@p one!