You'd be much better posting this in the Caravanning Abroad Section - where you should get lots more replies.
Tips - Norfolk Lines ferries are generally the cheapest, from Dover to Dunkerque, and have a promotional code, usually available at the time of the NEC caravan show, which could get you a ferry crossing for as little as £58.00 (we've just booked two return crossings for 2011). If you shop at Tesco you can save up your vouchers and exchange them for 'deals' at three times the value, and use these to pay for your Eurotunnel crossing.
Breakdown cover - Red Pennant from the Caravan Club is the Gold Standard - and really does offer a comprehensive service to caravanners but ADAC (a German company) is said to be the cheapest and most comprehensive and is recommended by a lot of contributors to the 'Abroad' sectiion.
Driving on the 'wrong' side is no problem - just remember 'Keep your bum in the gutter' and you'll stay on the correct side. Chant this when coming up to roundabouts, out of garage forecourts, and at junctions!
Traffic is less, and roads are better. There are toll autoroutes - which can mount up - but if you're cheapskates like us then you can avoid paying any tolls at all. Diesel is Gazole, Unleaded is Sans Plomb. There are more (and often better) Aires and picnic areas to stop at, most of which are very caravan friendly.
If you can, travel outside the peak weeks of mid-July to mid-August - sites are often cheaper, pitches are easier to come by, and facilities less stretched. Campsites are generally high quality. You can still 'tour' - ie without booking sites, and just going where you fancy when you fancy (outside peak weeks, anyway).
These are just brief tips, but if you need any more details I'd be happy to help - but I would suggest moving your post.