Why do many movie titles differ between the U.S. and the UK?

Why are
movies titled differently in the UK?

For example; >The Avengers changed to Avengers
Assemble.

Similarly href="http://www.imdb.com/title/tt1433562/" rel="nofollow
noreferrer">Vertige is called High
Lane.

What is the reason why so many
movies are retitled for the UK?

I know the reason why the
title of The Avengers was changed in the UK, but what is the
overall reason for changing movie titles for the UK?

Answer

The
UK is a different country from the USA, with a different culture, language, licencing
laws, censorship restrictions and different existing
properties.

Sometimes films in the US conflict with one of
those and get a very different release in the UK.

An
example is The Boat That Rocked - in the UK it got quite a clever poster that riffs on
the Beatles:

src="https://i.stack.imgur.com/VbrId.jpg" alt="The Boat That
Rocked">

In the US it was renamed to Pirate Radio and
the poster changed to include the love-interest and a boat full of girls (and is a
layout mess):

src="https://i.stack.imgur.com/kRH3t.jpg" alt="Pirate
Radio">

Yet another example is href="http://en.wikipedia.org/wiki/The_Madness_of_George_III" rel="nofollow
noreferrer">The Madness of King George III - it was renamed for the US
release because while Brits are used to referring to kings by numbers the Americans
aren't, so they didn't want to confuse audiences into thinking it was a
sequel.

They can make very odd marketing decisions too: the
film Couples Retreat got strange href="https://web.archive.org/web/20170201213613/http://www.mailonsunday.co.uk/news/article-1227868/Race-row-black-stars-airbrushed-Couples-Retreat-film-poster.html"
rel="nofollow noreferrer">racist posters the UK but not in the
US..

Fact is that the UK and US are very different markets,
so films get different names.