marvel cinematic universe - Why was the Avengers movie called something different in the UK?

In the UK the movie is called "Avengers Assemble"

Why was it given a different name in that market?

Answer

The Avengers was given a somewhat different name because of the British TV show The Avengers. The new name was to help keep them separate and to avoid any confusion for audiences in the UK.

Wikipedia says:

In February 2012, Disney announced that the film's title would be
changed in the United Kingdom to avoid confusion with the British TV
series of the same name, as well as its 1998 film adaptation, but this
led to confusion over the film's actual title. Empire magazine
reported that the film would be titled Marvel Avengers Assemble
while The Hollywood Reporter said that it would be called simply
Avengers Assemble.