Bryan - you will need a continental adaptor for your hook up - buy at any camping/caravan shop, also a polarity tester. (See other topics for details). You'll need a full set of bulbs for your car, a warning triangle, and a kit (or black tape) to alter your headlights to driving on the right. You'll need a reflective vest in case of accident - buy at Halfords. Get a good map (Michelin do a new one each year) and a good campsite guide - Alan Rogers (reviews and in English), Michelin (French, but lots of sites, including smaller municipals) or the Caravan Club. Nothing different about waste water - except sometimes the site (in the dryer South) ask you to use it to water the trees. Chemical loos are just the same emptying points as in England. Most sites have hook ups, even the smallest.
Stick something on your steering wheel - or get your passenger to chant 'Drive on the right, Drive on the Right, each time you go around a roundabout, come out of a junction, etc - or remember the saying 'Keep your bum in the gutter' (something mentioned in earlier postings on this site).
Don't take too much with you - remember the food and wine are excellent, and big supermarkets stock just about everything you could want anyway, even if you hanker for tomato ketchup, or baked beans. Try to local markets. And last, but not least, have a great holiday in a great country - like many others of us who use this website.