Over the summer, UK Visas and Immigration released new rules and regulations that came into effect on the 6 July 2018. This will impact Short Term Study Visa holders and applicants.
The changes mean that when applying as a short-term student, you must intend to leave the UK within 30 days of the end of your study (if it is before the date your immigration permission ends). If you do not leave the UK within this time, it could affect any future immigration applications to the UK (such applications could be refused and a time-bar applied if the Home Office believes you exercised deception about your intention in your short-term student immigration application). If your study (as stated in the letter you presented to the Home Office as part of your short-term student immigration application) continues until the date that your immigration permission ends, you must leave the UK no later than the date your immigration permission ends. (Source: www.gov.uk)