Brexiters have 'absolutely no plans' but there are a number of challenges that the U.K. economy will face through the process, Pascal Lamy former WTO Director General told CNBC at a conference in the south of France.

"I'm convinced it will take a very long time, first because we've got this so-called article 50, which is the sort of disentangling of the U.K. legislation from the EU legislation and that is square one. Once you've done that, and it will take a lot of time then you have to go to square two, which is the new relationship between U.K. and European continent."