Holidaying by ferry is really easy and hassle free! You don't have to worry about spending money on a rented car that you aren't used to, or about how, where and when you leave it back etc. Because, you have your own car with you!
Many ferry sites allow you to book your complete holiday through them and to your specification i.e. Hotel with or without pool, next to the beach or not etc.
For ferry holidays to France the leading ferry company is Brittany Ferries, they offer comprehensive holiday options. You can search for places to stay on there website which is very slick and easy to use. From there you'll see for yourself how good the variety on offer, with hotels available in every part of Spain and France (the two countries they sail to).
P & O, the largest ferry operator in the UK, also have a great network of places to stay. They offer hotels, B&B's etc. All over Europe, but they specialize in Amsterdam and Paris. And uniquely pleasing is their availability of beautiful château's all around France.