I had a bonded pair fall out and the vet bills to get them all stitched back together came to over a thousand pounds, no least because they decided to do it on a bank holiday Sunday, it would have cost me £160 just to see the emergency vet before they even did any treatment. They required general anaesthetics to get the stitches done, antibiotics, pain killers, further surgery when they pulled their stitches out, 12 visits to the vet. Petplan covered it all bar the £50 excess, I don't know what I would have done without.
You'll find lots of similar stories on the forums.
If you can afford it, I would get insurance, and then start a savings account, and when you have more than £1500 in savings, that's when you can afford to not have insurance. I worked out my insurance for Jeremy paid out in the year I had him 4 times what I had paid them for premiums.