Yes you might not believe it but Iran does have a British Embassy. The British embassy is located in Tehran and we have listed the contact details for this embassy below. Note that this is a Muslim country and hence the embassy is closed on Fridays however it is open on a Sunday. For more information contact the embassy as listed below.
The British Embassy in Tehran
198 Ferdowsi Avenue
Telephone:+44 20 7008 1500
Note that the British embassy will begin consular activities in Tehran on Wednesday February 24, 2016 after being closed since the Embassy was closed in 2011.