If you are applying for car insurance or already have a car insurance policy and it is due for renewal and you have an unspent conviction under the Rehabilitation of Offenders Act 1974 or you are subject to a prosecution that is ongoing then you will need to inform the insurer of this fact. However, the policy may be worded in such a way that you need to inform your existing insurer of the unspent conviction even if the policy is not due for renewal so you should check this. If your conviction is spent then you will not need to inform them in the above situations.
So, assuming that you have an unspent conviction, what is the attitude of car insurance providers in such a situation? Well, you may find that many insurance companies will refuse to provide cover in view of the perceived additional risk. If an insurer will not consider cover then they should at least assist you in finding an insurer that will cover you.
Those insurance companies that will consider providing cover are likely to charge you more for providing the cover so you should be prepared for this.
Do bear in mind that if you failed to inform the insurer of your unspent conviction in one of the above situations and the insurance company found out then they could cancel your policy leaving you to try to find another insurer that could be even more difficult or they could refuse to pay out should you claim on your car insurance policy.
You may find that some insurance companies may not be concerned about non-motoring convictions when deciding if they will insure your car. They may take a different view on those that have had a motoring conviction.
One of the ways of trying to find an insurer that will consider providing car insurance for someone with an unspent criminal conviction is to use the Internet to search for such providers.