If you use the routefinder here
http://www.viamichelin.com
you'll be able to see which places are along your route.
(To use the routefinder, you'll need to use the correct spelling of Boulogne-sur-mer).
If you want a stop roughly half way along your route, I suggest seeking a hotel in the Le Mans area.
Click on the 'Hotels' tab on the same website and enter your requirements. I've just tried a random date in August and been offered a choice of 28 hotels. The total price quoted for 2 people ranged from 32 euros to 250 euros. (So, whatever type of hotel you require, there ought to be something to meet your needs).
The list of hotels includes a map of the area so, if you particularly want to locate a hotel which is exactly on your route (rather than a few kilometres away) this should be quite easy. In particular, I note that the budget Formule 1 chain has their Le Mans Nord hotel conveniently situated. They charge just 28 euros per night per room (with up to 3 occupants).
http://www.hotelformule1.com/formule1/fichehot el/gb/for/2436/fiche_hotel.shtml
Chris