A6 Marseilles to Paris - where to stay?!

This year we are heading further south than we have done before - we finish our france trip just north org Marseilles.  We have to get to Cherbourg for the ferry home and are looking for an overnight, probably off the top end of the A6 or just off the A85. Can anyone help - it will be a very long day's drive, so the easier the better please.  many thanks