Class has very little to do with money. You can be a DotCom Billionaire and be common as muck, or you can be an aristocrat who's struggling to stop the roof collapsing.
Upper class: usually titled, don't really need to work to live, usually employs staff, some of whom live in.
Upper middle class (A): senior managerial. CEOs, directors, Fellows of professional institutions, Flag Officers. Privately educate their children. Employs a cleaner and maybe a nanny. Generally have some choice over their hours (some work 100hr weeks, others 30). Well paid
Middle class (B): middle management, doctors, headteachers, lawyers, bankers, Captains of aircraft and ships. Used to privately educate, can no longer afford to. Might employ a cleaner and have an au pair. Often have to work unpaid overtime.
Lower middle class (C1): teachers, clerks, accountants, clergy, junior officers, restaurant managers. Frequently work unpaid overtime.
Skilled working class (C2): Machinists, welders, nurses, train drivers, chefs, Senior Rates, plumbers. Often better paid than C1 as they get overtime.
Unskilled working class (D): supermarket staff, warehouse staff, restaurant staff, Junior Rates. Paid a pittance.
Underclass (E): criminals or long term unemployed.
Me? By most measures (choice of words, accent, interests, earnings) I'm middle class. In reality, I'm in a skilled working class job and swear like a trooper. As for what I call a toilet/lavatory, I alternate between "bog" and "khazi".