I Would think best place to ask would be a vet's its interesting someone has said Tesco I too throught they were good value but a quote I had for travel insurance from them was �107 More for an annual insurance than the one I got from a high street bank, banks probably do pet insurances.
Depends on what you want. A lot of pet insurances only pay on a condition for 12 months (Tesco?). Petplan covers condition for life; you have to pay excess each year but when you have a Persion with severe skin problems costing in excess of �1000 a year to treat over three years the excess doesn't seem so bad.
Petplan - the ones that you buy from tesco, etc only the cover the cat for treat needed in that year and not for any previous medical conditions. If your cat (heaven forbid) gets ill and needs long term medical care you will find it very hard to get insurance again. A lifetime policy is the one to go for. Mine costs about 10 quid a month.