Insurers want you to stay with them. After they have spent money on expensive advertising they don't want you to leave them for a cheaper company so they try to lock you into automatic renewals. If you refuse to let them do this you will be free to haggle, and quite often just ringing your current insurer, and telling them that you intend to compare prices, can result in a substantial reduction in your premium. If they won't give you a discount (and most will) then it's time to shop around.
Once you've found a more reasonably priced policy the new insurer will try to push up your premium by selling you extras such as legal representation or a free courtesy car in the event of an accident. These are often poor value for money and should usually be refused. Insurance sales staff can offer price reductions to tempt you to buy these but remember that when your next renewal date arrives you will be charged full price for them. In this way, that bargain priced policy can become an expensive one extremely quickly.
Do also bear in mind that one day you may be involved in an accident
and have to make a claim against your policy
. Some insurers are better than others at paying up quickly, with the least fuss. Before you actually buy that policy it may be a good idea to type the name of the insurance company into your favourite search engine and see what other people say about them.