Jon,
    I have made the journey lots of times, if you go motorway its fast but not cheap, from Calais to Tortosa one and a half to two days depending how fast you want to go and thats through Paris with a satnav.You can avoid Paris and go via Rheims which adds something like fifty miles to the run. Also you can take the Route National roads but be prepared for long hold-ups and convoys which you can't overtake easily if you have right hand drive,obviously this way takes longer but is more reasonable.Try and refuel off the Autoroutes if possible,much cheaper!
As for stopovers I favour the Logis de France because they are family owned small hotels and normally the food is very good. There is a catalogue which can be obtained from the French Tourist Office or if you find a Logis they have this free of charge on the counter. There are motels and hotel groups all the way down the autoroutes at all prices,Campanille,Ibis etc.........all can be found on the net as can Logis de France.
Hope this helps a bit.................any questions, come back!

                                                    Old Nelson.