You should not let your car insurance lapse and renew it immediately if expired. In case you renew it after expiry, the following outcomes may follow:
1. If you have earned any No Claim Bonus over the last few years of the policy period, you might lose the same.
2. After your insurance expires, your car is not insured and that may put you and your car at considerable financial and legal risk in case of any.
3. Having at least third-party car insurance is mandatory by law, so in case you are charged under the law for driving without valid car insurance, you will get fined or face imprisonment for up to 3 months.