If you are in Nicaragua or in Costa Rica as a British national then you will find the British embassy located in San Jose in Costa Rica. This embassy covers both countries in South America. If you need toin Costa Rica or Nicaragua then this is where it is done. You can also register a death or a birth at this embassy.
British Embassy in Costa Rica & Nicaragua
Edificio Centro Colón,
Paseo Colón and Streets 38 and 40