Insurance companies are changing their insurance rates all the time. Sometimes they raise them when there have been a large number of claims, and sometimes they lower rates when they are looking to pick up more clients. What all of this amounts to is that a cheap policy might just represent a market shift or a change in the needs of a particular company. In other words, don’t just give the hairy eyeball to all cheap rates; seek them out. Just make sure that the policy represents your needs well.
Motor insurers in the UK place a limit on the amount that they are liable for in the event of a claim by third parties against a legitimate policy. This can be explained in part by the Great Heck Rail Crash that cost the insurers over £22,000,000 in compensation for the fatalities and damage to property caused by the actions of the insured driver of a motor vehicle that caused the disaster. No limit applies to claims from third parties for death or personal injury, however UK car insurance is now commonly limited to £20,000,000 for any claim or series of claims for loss of or damage to third party property caused by or arising out of one incident.
Comprehensive insurance covers all of the above and damage to the vehicle caused by the driver themselves, as well as vandalism and other risks. This is usually the most expensive type of insurance. It is custom in the UK for insurance customers to refer to their Comprehensive Insurance as "Fully Comprehensive" or popularly, "Fully Comp". This is a tautology as the word 'Comprehensive' means full.
But liability coverage levels come in threes — you’ll probably see something like 50/100/50 up to 250/500/250 in typical policies. You can think of these limits like: individual injuries / total injuries / property damage. Insurers are a little more technical, calling them bodily injury liability, total bodily injury liability and physical damage liability.