Does anyone know the origins of British Jews? Are they Ashkenazic, Sefardic, children of recent immigrants?
Inquiry into the First Settlement of Jews in England
Menassah ben Israel's Plea to Oliver Cromwell to re-admit the Jews to England
Largely Ashkenazi. The oldest communities were Sephardic but they made up very small numbers. Moses Montefiore was elected Sheriff of London in the 1830s and of course Disraeli, a baptized Jew, was Queen Victoria's favorite Prime Minister.
http://en.wikipedia.org/wiki/History_of_the_Jews_in_England
There were large waves of working-class Jewish immigration from Russia and, unlike the U.S., the Netherlands into London's East End in the late 1800s and early 1900s. The wave of refugees from Germany and Austria in the 1930s was proportionally much greater in Britain than in the U.K., as well.
The Jewish communities in Britain are even more highly centralized than they are in the U.S., with most Jews living in London and a smaller community in Manchester, and insignificant communities elsewhere. Provincial Jewry in Britain has declined significantly in the past 100 years as people left the north for the southeast.
Given that British Christians have largely drifted away from churches and have smaller families than Americans, it should come as no surprise that British Jews have experienced the same trends at even higher rates.