1. People tend to be very time conscious in the UK. Lateness (more than 5 minutes for work/study appointments, more than 10 minutes for social) is considered rude. Tutors, doctors and other professionals may refuse to see you if you arrive late.
2. Shops and office closing times are strictly adhered to. These are not generally the times at which the last student/customer will be admitted. They are the times at which business ceases. If you need 15 minutes to complete a transaction, the service is likely to ask you to "come back tomorrow" if you arrive 5 minutes before closing time.