The TUC have decided 24 February is Work your correct hours day. To help decipher the extremely complicated idea of unpaid overtime they've added to their website

 http://www.worksmart.org.uk

Which advocates working out how much you subsidise shareholders with unpaid overtime

 http://www.worksmart.org.uk/overtime_calc.php

type in the appropriate numbers and it tells you how much your employer would owe you if they were honest.

as I said I only robbed the link. And unpaid overtime is not complicated. It's called Slavery.