It is your responsibility to ensure that you comply with the conditions of your visa at all times.
If you have any queries or concerns about your immigration status, you should contact the Immigration Advice Service.
Your responsibilities include ensuring that you do not stay in the UK beyond the expiry date stated on your visa, unless you have made a renewal application. You must also adhere to the work conditions of your visa. Failing to comply with the conditions of your visas is a criminal offence and could result in your visa being withdrawn.