Stops wise what you looking at Calais to maybe Bordeaux area for first stop then on to somewhere mid Spain for the second stop? When I rode to Spain in 2016 with my mate we stopped overnight at Le Mans then a small village near Bordeux. Then half a day to Jaca, crossing the border via Pau. We never touched a motorway on the way there but it rained pretty much all the way which made it a very, very, miserable ride. On the way back we did it by motorway and got to Calais in 2 days. We camped, no hotels. So that's 4.5 days getting there and back. Taking into account petrol, toll charges on motorways, campsite costs, daily living expenses etc. it would been cheaper getting a ferry. That would be my choice next time for sure.