Driven to France, Netherlands, Germany, Switzerland all with the GTI. Last time coming back from paris did 200km/h all the way to Calais (had to get out of that dump paris) but don't take my example, going that fast can get the car impounded... I hadn't eaten for 26 hours and slept for only about four and was quite eager to get back to Calais.
Anyhoo, speeding aside, make sure you carry hivis, safety triangle, first aid kit and fire extinguisher... that's the law. Also a few bottles of water are just nice to have. If you have a "europlate" like my car you don't need to have a GB sticker (I dislike GB stickers anyway). Ehm what else... make sure you have headlight deflectors, unless you've got xenons, in which case a few moments with a torx screwdriver will sort you out.
Otherwise remember to drive on the wrong side, and if you're like me have plenty of anecdotes about the country you're passing through to bore your passengers with.