If you have completed a course at the University of Birmingham and your current Tier 4 (General) visa has not expired, immigration rules state that you must not start a new course of study until you have made a new application for further Tier 4 leave.
If you completed your previous studies and are now starting a new course
You should be able to register on your course and commence studies if:
You have been assigned a CAS by the University of Birmingham for your new course of study.
You make a visa application before your existing permission to stay expires
You can demonstrate that you have made an application for a new Tier 4 (General) visa.
If you did not complete your previous studies and are now changing to a different course
You will be able to use your existing Tier 4 visa to start your new course providing it is at:
The same level as the course you were previously granted a visa to study; or
A higher level than the course you were previously granted a visa to study; or
A lower level than the course you were previously granted a visa to study, provided the conditions and requirements of your permission to stay are the same as they would be given if you made an applciation for your new course.
If your new course requires ATAS you must obtain ATAS approval before you can start your course (or period of research).
If your new course is shorter than the previous course, you will need to notify UK Visas and Immigration (UKVI). UKVI may reduce the length of time on your student visa.
If your new course is longer than your previous course, you are likely to have to make an application for an extension of your student visa. You should do so as soon as possible, and certainly before your current visa expires, in order to complete your new course.
Sources of help
The ISAS visa pages provide information on how to apply for new visa including the forms you need to complete, help available and when to apply.
If these pages do not answer your immigration query, please submit an online query to ISAS.