We don't have to extend our car insurance cover if we go to Europe - read the back of the ins cert and it will (should) tell you there about driving in Europe. We are fully comp
For holiday insurance we also use Insureandgo
If you have AA breakdown cover for the UK you will find it costs about �40 to add European cover. Can I recommend (highly) Call Assist?
http://callassist.net/index.aspx?page=terms
We have violet cover for just under �20. Our car broke down in France (clutch went) and under this colour policy we only paid for the new clutch. Call Assist arranged everything from breakdown lorry to collect the car to getting us a taxi back to collect the car once it was fixed. The also called us everyday to make sure we knew the state of repairs, cost etc etc. The also refunded our extra travel and accommodation costs