Re: a more neutral term (two cents)
Maybe "plebeian" might work, but isn't the proletariat supposed to be the salt of the earth? I'd associate "proletarian" to "working class", without the "trashy" connotations.
The problem with Mrs Claire's definition for me is that "trailer trash" refers to a specifically American subculture, so I don't know if it's the most appropriate term to definine a European subculture/social groups.