If your visa is due to expire before you have finished your course, you will need to apply for an extension.
If you have a Tier 4 Visa you must be present on campus for the purpose of your studies during term time, unless you apply for, and are granted, an authorised absence.
It is your responsibility to keep the UK Border Agency up to date with your personal details.
Students from certain countries need to register with the police within seven days of arrival, and update the police on any changes in their circumstances
You will need to apply for a general (tourist) visa and may need a letter from the University to confirm the date of your graduation.
If you are leaving the UK for a trip, you will need to think about the relevant visa application(s) in advance.
As your Tier 4 visa sponsor, the University is obliged to monitor your attendance and progress on your course and check you are not doing anything which breaks the conditions of your visa.