Can is be that France and UK do not account for colonies?

Present colonies? Sure. But France doesn't have that many colonies left. Former colonies? Unthinkable.

I think this explains it: France had a mess on its hands before 2000. And immigrants have a way higher birthrate, so the issues grow exponentially.

That said, this graphic does not account for two things:

1. the more unlivable a place becomes, the more people leave - and thus the lower net migration will appear. If a million natives leave and are replaced with 1 million Muslims, this will appear as 0.00.
2. The lowest being 5% of your population being the result of extra immigration is still astonishingly high. For France, it is 3.5 million. That said, I think a significant part of that will be from within the EU and thankfully for France, it's not a highly sought destination for immigrants like Germany and the UK are.