Sian has always been a keen supporter of community charities both in the UK and overseas. Before moving to Cambridge she worked as a volunteer at SANEline, a telephone helpline for the mentally ill and their carers. She is a longstanding supporter of, and has visited, the SOS village for AIDS orphans in Swaziland.

After being elected to Cambridge City Council in 2002, Sian became a founding trustee in 2004 of the Cambridgeshire Community Foundation. The community foundation model, which was pioneered in the USA, provides an umbrella charity to encourage and manage giving to local community groups.

The Cambridgeshire Community Foundation, which also covers Peterborough, now manages 20 charitable funds, and has awarded grants totalling over £3.2m to more than 1100 local projects.

It is the aim of the Foundation to reach even the smallest local voluntary groups, those without professional fund-raisers, who have difficulty competing with national charities for necessary funds.