I don't know if this helps add some shade to the distinction, but the National Readership Survey's social grading categories at least attempt to address the complexity. See if you can pigeonhole yourself!

A. Upper Middle Class: Higher managerial, administrative or professional.

B. Middle Class: Intermediate managerial, administrative or professional.

C1. Lower Middle Class: Supervisory or clerical and junior managerial, administrative or professional.

C2. Skilled Working Class: Skilled manual workers.

D. Working Class: Semi and unskilled manual workers.

E. [Untitled]: Those at the lowest levels of subsistence, casual or lowest grade workers, pensioners and others who depend on the state for their income.

I think "E" is the "underclass", but they're too courteous to use the term.

I appreciate that this is all quite tiresome for many, but I like categories, that's why I'm a librarian. And as such I've been intrigued to read on more than one occasion that folk song is a product of the working class which has been adopted by teachers, librarians, etc. who have no natural connection with the songs because they're "middle class". I think that's unfair and inaccurate.