St Pierre & Miquelon is a Territorial Collective (Collectivité Territoriale d’Outre-mer) of France. If your passport describes you as a British Citizen you will not need a visa to enter St Pierre and Miquelon. Other British passport holders should check the current entry requirements on the website of the French Ministry of Foreign Affairs and if necessary confirm with the nearest French diplomatic mission.
Your passport should be valid for the proposed duration of your stay. No additional period of validity beyond this is required.
The French authorities have confirmed they will accept British passports extended by 12 months by British Embassies and Consulates under additional measures put in place in mid-2014.
UK Emergency Travel Documents
UK emergency travel documents are accepted for entry, airside transit and exit from St Pierre and Miquelon.