I cannot arrive on time/am still waiting for my visa.

The deadline to arrive is set based on the date given to the UKVI for your course. If you're experiencing delays due to visa matters, raise a ServiceDesk ticket with your Student ID to the Immigration and Compliance team and indicate when you expect to receive your visa and travel to the UKVI. They'll review your case on a case-by-case basis to provide the necessary assistance.

Raise a ticket Here.