Jim,
The Board of Deputies of British Jews represent some of the Jewish community only

Most actually.
Enough to make it anti-Semitic to say parties should not talk to them (they all do), or to link them with staged protests against Corbyn or to terrorism as Dave does.

"The Board of Deputies is the only democratically elected, cross-communal, representative body in the Jewish community.   It comprises nearly 300 deputies directly elected by synagogues and communal organisations, from youth movements, to social welfare charities and regional councils.
In addition, there are also a number of under-35 observers, appointed by synagogues and organisations to supplement their representation and to ensure that a new generation of communally minded activists can contribute to our work on behalf of the community.
Each synagogue and institution elects one or more Deputy, depending on the size of that particular body, with elections occurring every three years."