But seriously, I have been asked for my V5 document at the border crossing into Switzerland. The border between France or Germany and Switzerland is still a full time check-point and the border police are quite like to check your documents and I have also been asked to show my spare pair of driving glasses - So be warned!! Much better to be prepared than be refused entry into Switzerland.
The other thing to consider is of course is insurance. If you break down for any reason Audi Assist will help, but if you did happen to have an accident and your car was not drivable, how would you get it home? It's well worth taking out breakdown/accident insurance. You can do it at the Channel Tunnel as it will only cost a few pounds but could save you a lot of money.
I know from bitter experience. I had a previous Audi written-off by someone crashing into the back of me when I was stopped at traffic lights. There is more to taking a car to Europe than just getting on a ferry!
Also remember than the alcohol limit in almost all EU counties is half what it is in the UK, so definitely don't drink and drive. Random testing is also allowed. Be aware of what the French signs for speed cameras are as they do have cameras on the Autoroutes as well. Their is at least one between the Channel Tunnel and the A26 to Reims. They don't paint theirs Yellow and the one-the-spot fines can be high.
Not trying to be a kill joy but as I said earlier, better to be prepared that fall fowl of, especially, the French police.