Yeah I was back a couple of weeks ago
The holiday turned out a little different to how we expected though, less driving and more drinking . I went with my best mate - I could never sit with the missus in the car for that long
The zed was actually really comfy and I didn't really stop for any driving breaks other than the ferry crossings and to sleep.
Petrol in France was about 1.30 euros so its not THAT bad.
As for the number plate, I think as long as you have a GB magnetic sticker you are okay. I didn't have any brushes with the law at all, in fact I think we only saw 2 police cars the whole trip. The speed cameras are pretty hidden though, just concrete blocks and no road markings so you dont really see them till you have gone through them.