This information is of relevance to you if you are allowed to work during and outside term time, not if your work permission is limited to work placements.
Most Students and Child students have immigration permission that extends beyond the end of their studies. You can work full time for this extra period once you have completed your course, but you may not be able to work at all if you have not finished your course. There are some exceptions from the usual restrictions if you make an immigration application to 'switch' into a work route.
Moving into a work route
If at the end of your course you apply to stay in the UK under a work route, you can usually work full time until your work application is decided.
Normally, you must not take work that your work condition prohibits. However, if you have Tier 4 or Student permission, your work condition allows you to start a Skilled Worker job after you have applied for Skilled Worker permission and before the Home Office makes a decision on that application, even if the job is permanent, full time and/or requires work as an entertainer or professional sportsperson. You can start your Skilled Worker job up to three months before your course end date, but no earlier. This means that if you apply for Skilled Worker permission after 12 months of study towards a doctorate, you will usually need to wait for a decision before starting the job.
Similarly, if you have applied under the Start-up route, you can start your business before you receive a decision from the Home Office on your application.