Please note that the head office of British High Commission in Nigeria is in Abuja. The office in Lagos is known as the is the Deputy British High Commission. Here are the contact details:
Deputy British High Commission, Lagos
11 Walter Carrington Crescent
Victoria Island
Lagos
Telephone: (00234) (1) 2619531, 2691537, 2619541
Email: consular.lagos@fco.gov.uk
Office hours: 8am – 3.30pm Monday to Friday (Nigerian time)