St Pierre & Miquelon is a French Overseas Territory. There’s no formal British diplomatic or consular representation. See British representation
Most visits to St Pierre & Miquelon are trouble-free.
Although there’s no recent history of terrorism in St Pierre & Miquelon, attacks can’t be ruled out. See Terrorism
The European Health Insurance Card (EHIC) doesn’t provide any health cover in St Pierre & Miquelon.
Take out comprehensive travel and medical insurance before travelling.
Source Article from https://www.gov.uk/foreign-travel-advice/st-pierre-and-miquelon