Jam and Jerusalem is a fairly well-known phrase in British English (there's a BBC sitcom starring Dawn French and Joanna Lumley with that name). It is associated with the Women's Institute (WI), a membership organisation for women in England, Wales, the Channel Islands and the Isle of Man (Scotland and Northern Ireland have their own organisations). The 2003 film Calendar Girls, which stars Helen Mirren, is about a village WI group, and one of the characters in the film says "it's not all jam and Jerusalem, you know", meaning that the group gets involved in all sorts of activities, not just the traditional jam-making and patriotic hymn-singing.
The Women's Institute in England and Wales was founded in 1915 (based on the Canadian organisation founded in 1897) with the purpose of involving rural women in the war effort. The words "jam" and "Jerusalem" hark back to the organisation's wartime origins. Jam, because the women canned or made jam to feed the population, and Jerusalem after the patriotic hymn (poem by William Blake set to music by Hubert Parry in 1916) which was also associated with the Suffragettes.
Jerusalem is still sung at WI AGMs, but each local group can decide for itself whether to sing it at meetings. I often speak to WI groups (on the subject of language or dictionaries) and have only ever heard it sung once. It may be sung today at a conference when the UK's minister for women, Harriet Harman, will ask WI members to help crack down on sleazy ads in local newspapers. (I blogged on the origin of the word "sleazy" here).
The WI's website includes an explanation of the phrase "jam and Jerusalem".