As a registered Charity, Newman Students' Union operates under its Constitution and Bye-Laws. Imagine this as the "rule book" for how the Students' Union manages itself. The Constitution and Bye Laws are approved by the Members (students) and by the Board of Trustees, and are also available on the Charity Commission website.
You can read or download the full document below, or you can also download individual Bye-Laws for the specific information you are looking for.