That very cheap car insurance may not be as cheap as you think!
You scrimp and save to pay for your car insurance but at last it's done so you sit back and think OK, no more to pay out for another year. Then after a few months you change your car (why not, most people change theirs every three years), you have a bump, change your job, moved to a new address, or any one of dozens of circumstances that you need to tell your insurer about, otherwise they could nullify your insurance.
You ring them up (always assuming that the company you chose actually has a telephone line, and that there is a real human to answer it) let them know your change of circumstances and two weeks later a bill arrives for £120. "They can't do that!" you cry. Oh yes they can, and often do. It's all written down in the terms and conditions. You DID read the terms and conditions before buying the policy, didn't you?