I don’t quote the CIA. Never even looked at their book.
https://www.cia.gov/library/publications/the-world-factbook/geos/uk.html
But like I said, the CIA’s figures from the U.K. are dated.
Germany and Denmark also estimated, each, their Muslim population to be at about 4%.
“Very interesting” (Arte Johnson in “Rowan & Martin’s Laugh-In”).