Do it regularly in car from near Benidorm to both Le Havre and Boulogne.
Leave 8.30am and get to Boulogne 6.30am next morning for 9.15 ferry.(Including a few stops for coffee and powernaps)
Did Le Havre on bike in March.
1.30pm from Benidorm .... F1 Pau 9.30pm ..... left 7.00am and arrived Le Havre 4.30pm for 6.30pm fast ferry.
I can do it from just South of Barca to Le Havre in 13 hours with a bike trailer on the back of the car.... Would allow another 3 hours from Valencia.
Its a long drag if you are the sole driver though....I usually get through 2 boxes of 'Pro Plus' tabs and two or three black coffee's.... I find the trick is to keep going on the limit rather than fast stop-start runs.... peage's are a pain in the butt mind!