Low-class and Non-U

Low-class adjective - Occupying the lowest socioeconomic position in a society.

Non-U and low-class are semantically related. In some cases you can use "Non-U" instead an adjective phrase "Low-class".

Non-U adjective - Not characteristic of the upper classes especially in language use.

Low-class and non-U are semantically related. You can use "Low-class" instead an adjective phrase "Non-U".