If you require consular assistance for any reason whilst in Russia and there is no diplomatic office in the city where you are staying, you should in the first instance contact the main British Embassy in Moscow, who will be able to provide assistance to you should you need it as well as advice about your nearest representation.
British Embassy
Smolenskaya Nabarezhnaya
Moscow 121099
Telephone: (7) (095) 956 7200
British citizens need a visa in order to travel to Russia, and this must be arranged through the Russian Embassy in London prior to departure.