If one Muslim person entered last year, two entered this year, and four the next year, then you will see an annual growth rate of 100 percent.

British Muslims generally tend to be from Mirpur, in Pakistani Kashmir. It is a regressive part of Pakistan, and they have carried their culture over. Along with the segregation they faced in the 1960s ("Rivers of blood" speech by Enoch Powell, or the "Tebbit" test), the ill effects of those decades are showing up now.
 
As I have pointed out earlier, the highest homicide rates are from Christian countries (Disclaimer: I am neither Muslim nor Christian). Perhaps you want to worry about that fact? There are plenty of real issues to worry about, compared to the opinion of British Muslims on Sharia. I don't spend all my time worrying about the opinions of the Amish in Alberta or fundamentalist Mormons in British Columbia.