London is about 4 times bigger than Saint Vincent and the Grenadines.

Saint Vincent and the Grenadines is approximately 389 sq km, while London (including the 32 boroughs of greater London) is approximately 1,572 sq km, making London 304% larger than Saint Vincent and the Grenadines.
Tip: This to-scale comparison of Saint Vincent and the Grenadines vs. London uses the Mercator projection, which distorts the size of regions near the poles.