t4在学期结束后可以全职工作的 只是不能签permanent contract而已
http://www.ukba.homeoffice.gov.uk/visas-immigration/studying/adult-students/conditions/
…
you are allowed to:work for up to 20 hours per week during term time;
work full-time during vacations;
…
…
If you are allowed to work, the work you do must not fill a full-time permanent vacancy
…
…
If you are allowed to work, you can work full-time during vacations within the above limits. If you have completed your course and you apply to remain in the UK under the points-based system before your existing permission to stay expires, you can work full-time (within the above limits) until your application is decided.