If you need to self isolate during the academic term, you will need to inform the Student Support Officer or School Departmental Administrator. It is best to do this by email so that there is a record showing the reason for your absence. If your absence means you will miss an exam please refer here.
If you let your friends/family know you are self isolating then they know not to visit but can hopefully help with anything you need including getting food delivered.
You should also follow the guidelines on the NHS site in relation to your own personal health and what steps you need to take.