I suggest you get the stromriders guide to europe, available in surfshops and from
http://www.lowpressure.co.uk It has good info on France and Marocco, most if not all the info you want.
The Anglet/Biarritz area is packed with surfshops, surfrentals, surfschools and shapers. It should be real easy to find a board to rent. I guess you'd be better off buying one there tho, renting sounds a bit expensive in the long run.