Just a point about your sister's old van - you'll find MOST french vans are much older than ours, and much smaller - usually still the square boxy glass-window type. She won't look out of place at all, in fact should fit in rather better than anyone with a posh twin-axle, end bathroom job! Pitch sizes, generally, are bigger than in England - and some are just enormous. The price you pay for a pitch includes the whole pitch, and you can put whatever you want on it, usually. We've had caravan, awning, car, and two pup tents on pitches before today. You shouldn't have a problem - but if you have a twin-axle then let the site know - some sites have 'no twin axles' policies but can make exceptions when they know you are a genuine 'caravanner' and not a 'traveller or itinerant'.