If you already have insurance, you should be covered for the minimum cover.........ie third party only in Europe, but if you're looking to buy insurance, Norwich Union direct are a good company and may include European breakdown.
If you've got a crappy car as you say, that's all you'll need (TP only), and I'd agree with Drowning and say get yourself some European breakdown cover. It's expensive, but worth it.
But they dont normally cover vehicles older than 10 years old (or something like that)
I've been down through France and Spain a million times, so if you need any more info, let me know just ask