Complex sentence: Some people adopt the accent as a means of "blending in", appearing to be more working class, or in an attempt to appear to be "a common man" sometimes this affectation of the accent is derisively referred to as "Mockney".
Split into simpler sentences: Some people adopt the accent as a means of "blending in" to appear to be more working class or in an attempt to appear to be "a common man". That affectation of the accent is sometimes derisively referred to as "Mockney".