i drive france 3 times a year normally and stay in reasonable priced hotels off the motorways situated at nearly every major town........
www.fasthotel.com and
www.villages-hotel.com are two types of great accomodation for about £20 - £25 quid a night
try
www.accorhotels.com as well because they do all the full range of hotel rooms from £10 a night to about £75 a night..all excellent
all in all roadside hotels put ours to shame in all ways (apart from full english brekky)
if you have time take the Route Nationales rather than the motorways , apart from the fact they are free , they are more scenic.
the drive is long but great.....avoid the peripherique on a friday or saturday morning apart from that the roads are bliss all the way through france