We are going to drive a campervan around Europe. What are the best maps for us to get hold of?

We are taking six months, and will be visiting about 17 countries….We are going to get Lonely Planet guides for all the countries we are going to….but I am not sure what are the best maps. We will need good detail on roads…I guess thats obvious….but does anyone have any recommendations?
thank you for pointing that out, we are both British so no problems there. We could take six years if we wanted!!