Spend some time with Google Maps. Streetview is brilliant for showing you the type of road you'll be riding.
There's no more human misery in Calais than anywhere else - the French authorities have removed The Jungle, through which you wouldn't have ridden anyway.
Here's a route from your place to Dover - take a look at the ascent, 1,100 metres over 80 miles. Have a think about how long that will take you, including mechanicals, lunch stops, etc. Then add four hours, and that's when you'll arrive in Dunkirk.
Here's a route from Calais to the cemetery
and
here's a route from Dunkirk to the the cemetery
Not much in it and the final bit's the same anyway.