Lol what utter crap. We're an island on the far edge of europe with stable borders and for more or less the last thousand years. On one side we've got relatively stable france and the other is the ocean. Compared to most of the world, movement into the UK has been very low up until the modern period. Historically major cultural exchange came from migration and invasion. Prior to the last ~200 years we haven't had either since 1066. The effect of the empire is vastly over estimated, look at early 20th century britain and you'll see very little cultural exchange outside of london despite the empire having already peaked. The average british town was overwhelmingly traditionally british until very recently.

Greece on the other hand sits in a part of the world which has more or less continuously changed hands for ages and it wasn't even a country a few hundred years ago. Greece's location makes it a crossing point of ideas between europe and asia.

This idea that we have a particularly multicultural history is fake history. Some parts of the world have single wave after wave of major change. We've seen little things filter through into urban trends but most of the country hasn't changed much.