I initially thought Animal Friends were great, they were one of the few insurers who would cover a 16 year old cat that I had adopted from a shelter. Made a couple of claims over 3 years, probably totalling no more than £1200, and the premiums barely increased. Then he got sick again and after a raft of tests and a spell at the vet for 5 days, I made a claim for £1750. The claim was paid, as were all the others, no problem. However at the next renewal date the premium more than doubled from £15 to £32 a month. Unfortunately my cat passed away before the higher premiums could kick in...but be aware of the possible premium increase with Animal Friends. I used Pet Plan for my others cats and despite once claiming £7000 in one year for one my cats, the premium only ever increased by a couple of quid at the most.
Once you are with a pet insurer you are stuck with them, as any new insurer will exclude any pre-existing conditions, so the option to move to another insurere if the premium increase is unaffordable is removed - so choose wisely, and don't use a company who will double the premium year upon year should you be unlucky enough to make a large claim.