Britain is blessed with a temperate climate, that means many plants can be grown here, that could not survive in parts of the USA, that get hotter summers, but colder winters. Most parts of Britain are at least 8a cold hardiness (the higher the more tropical), in contrast states in the USA with similar or hotter summers, such as New Hampshire, due to their snowy winters, can only grow plants that can survive to 5b. This means we can grow quite tropical plants, that have a bit of cold hardiness, that would not grow in places like New Hampshire as they would not last the cold winters.
Coastal areas, such as Cornwall, are even milder, with a classification of 9b. That is the same, or even higher than many parts of Spain!
Here are some plant ideas for a temperate tropical garden.