I rode from Fleet (Hants) to Paris last September, via Portsmouth. We got the overnight ferry to Ouistreham then routed down through Lisieux, Bernay, Evreux, Versailles then in to Paris, about 150 miles.
Our pace was very leisurely as it was a group ride of 40 people of all abilities. The France leg was 3 days which was way too long, 2 days would be about the right balance between seeing the towns and going at a decent pace to feel like you stretched yourself. 150 miles in a day would be too much IMO.
It was an amazing trip and surprisingly hilly, in places extremely hilly which I really did not expect. Heavy traffic around French cities on a weekday is a pretty unpleasant experience, so I would recommend doing the last 30 miles in to Paris on a Sunday if possible.