your usual insurance policy automatically covers you third party throughout europe, and there's no need for a green card anymore. you should bring the V5 with you and keep with you in the car at all times. the same with your insurance cetificate and driving licence.

depends where in europe you are going, but in some countries some items are compulsory, e.g. triangle, buls, fire ex, flourescent warning vest etc.

unless you have separate travel insurance, taean e111 form with you as well. that will get you any medical treatmet that you need i europe, paid for by the nhs. without that, you will have to pay everything first, and if that includes a helicopter ride off the nuerburgring for instance, it won't be fun, and it won't be cheap.

hope you make it to the 'ring this year. would like to see you and your motor there