I think the rule is this: if your vehicle is considered roadworthy in one country as evidenced by passing a roadworthiness test, called an MOT test in the UK, C

I think the rule is this: if your vehicle is considered roadworthy in one country as evidenced by passing a roadworthiness test, called an MOT test in the UK, Contrôle Technique in France, ITV in Spain (those are the ones I know) it will qualify for insurance. If it has passed a qualifying roadworthiness test, and is insured in one country, that is legally valid throughout Europe. There is in fact a larger agreement regarding insurance and roadworthiness that some nearby countries such as Morocco and Turkey also participate in, I'm afraid I don't recall its name right now.