I'll try as best I can to enlighten on this.
The Maire of any commune (district of Paris equals one) is called god. The Maire is elected - but the Maire's salary depends on the number of inhabitants. There are many angles, but that should give you the idea. This is why some of the tragedies of houses being erected on dangerous flood plains have happened as recently as last year.
Contingency plans certainly have to be made, though I doubt if the (inevitable i.m.o.) result of 'We shall fight them on the beaches' will be acceptable. With my hard-headed, historian, hat on, this is a likely result. How will our accommodating populace react to that? Another question, sorry.
Answer to OP. I think it is beginning to dawn on our leaders that we are in deep schtuck and hope contingency plans are being drawn - I worry that all the youngsters have been taught to be accepting of other cultures to the degree of neglecting our own. :(?