This page explains the work you are allowed to do while you are studying as an adult in the United Kingdom.
You can work part-time during term time, as long as it is no more than 20 hours a week, and full-time during vacations.
You can work on a work placement that forms an assessed part of your course as long is it is no more than 50% of the total length of the course in the United Kingdom.
You are not allowed to be self-employed, employed as a doctor in training (other than a vacancy on a recognised Foundation Programme), employed as a professional sports person (including a sports coach), as an entertainer or to fill a full-time vacancy.
Your can work as a student union sabbatical officer for up to two years. See Type of study and work placement I can do for more information on the work you are allowed can do as a Student Union sabbatical officer.
As an adult student, you are allowed to work:
The work you do must not fill a full-time permanent vacancy (other than on a recognised Foundation Programme), and you must not be self-employed, employed as a doctor in training (other than on a recognised Foundation Programme) or as a professional sportsperson (including coach) or entertainer.