The EU and particularly France and the UK have a refugee problem which is rapidly getting out of control. Let’s say that in Calais the French and UK police manage to stop any migrants getting near the Channel tunnel. This will lead to a steady build up of more and more people squatting in and around Calais. The flow of refugees from Africa and the Middle East is accessing the EU far away in the South so stopping the flow at Calais is not going to stop the EU ingress.
However doing nothing will only make the flow increase. Apparently millions of people around the world are on the move filling refugee camps in the Middle East and elsewhere. It is like an unstoppable force of nature. Maybe not stoppable but it can be better managed like the rechanneling of a river. Taking in refugees at one end, preparing them for another life elsewhere and then letting them move on.
I can only tentatively suggest that Europe has to create accommodation for refugees, work with their existing skills and add to them through education and training to make them citizens that other countries will wish to take on. For example the UK is importing huge numbers of nurses from countries which can ill afford to lose them. If the UK created a surplus of nurses through refugee training, those countries might not lose out so badly.
As it is the current UK and French policies are counterproductive, absorbing huge resources of money and manpower and not solving the problem.