Eurotunnel or Ferry?

http://www.norfolkline.com/

 DFDS seaways    usually the cheapest

completely variable, you must check all 3 ferry companies and tunnel. cheapest you ll get is 30 return

And I must add that after checking the prices in GBP on the Anglophone section of the website then delete cookies etc and go back and be French speaking.  Rarely have I not paid less, especially with Eurostar and Eurotunnel, even DFDS.