I use Insureandgo.com, I looked into the options in detail a few years ago when I got my cats, and they offered the best deal at the time. Read the small print about whether they continue to insure year on year per event as some companies will stop covering one 'claim' after £x or one year - which is no good for long term illnesses. Also - bear in mind that you are unlikely to get cover for an existing issue, and also not for dental work (unless caused by an accident).
I use Insureandgo.com, I looked into the options in detail a few years ago when I got my cats, and they offered the best deal at the time. Read the small print about whether they continue to insure year on year per event as some companies will stop covering one 'claim' after £x or one year - which is no good for long term illnesses. Also - bear in mind that you are unlikely to get cover for an existing issue, and also not for dental work (unless caused by an accident).