UK vehicle insurance policies provide minimum 'third party' cover across the EU. However, supplemental benefits (eg theft and damage cover) may not apply - so it is necessary to check with the insurance provider.
While you need valid insurance when driving abroad in the EU or EEA, you do not need to carry a green card (ie proof that you have vehicle insurance when driving abroad) certificate.
You may need to carry a green card to drive in other countries (eg Russia and Turkey). You can get a green card from your insurance provider. Bear in mind that you may also need additional insurance for your vehicle, trailer or caravan.
In other countries, it may be necessary to obtain additional insurance to show that you’re covered. You should check the travel advice for the country you’re driving in for more information.
For information about how to deal with road accidents outside the UK, see Citizens Advice.