Long after I did French at school, but long before I came to live in France, the Asterix books (the original French editions) were useful to me in learning more conversational French. Apart from all the historical jokes and mock-Latin, there is a lot of good French in them too -- and not the kind of French you used to be taught at school.
The English translations are very cleverly done, but naturally the jokes and puns are often different -- you can't usually translate jokes literally.
Andrew, is it possible to get the comics in Ireland. I lived in France for over 5 years when I was younger - I am now nearly 49 - and I have read almost all the Piere Tomal comics, absolutely hilarious stuff. But if it's possible the get Asterix And Obelix then I'd be made up. My kids would love them too.