Compared to the U.S., Britain is a small country. The reach of UK police is everywhere and an indiscreet tweet or Facebook post will have the Bobbies at one’s door. The head of the arresting detail will probably be Muslim.
By the way, Britain and the U.S. now have about the same number of Muslims inside their borders, around 3,400,000 each. Look at the difference in country size.
As for Brexiteers, they’re not the ones in the driver’s seat.