I think many Brits don't appreciate how highly respected the BBC is around the world, especially BBC news.
Our legal system, on which many other countries based their own.
Street fashion and the different 'tribes' - doesn't exist in the same way in other European countries.
Theatre, dance, literature, music of all genres.
Sense of decency and tolerance of eccentricity.
Ancient hedgerows - make our countryside unique, provide habitats for so much wildlife.
Cottage gardens (in fact English gardens in general)
The English language, now a global language, we're incredibly lucky to have it as our first language.
British universities - respected around the world.
British inventions - too many to list
Country churches, dry-stone walls, tea-rooms, picnics, cricket on the village green, bluebell woods, chalk downland, sweet peas, allotments,
But also, the London Underground, free museums and art galleries, vast range of cuisines from different cultures, the way London is a patchwork of villages.
British TV - only appreciated how good it is when I lived abroad.