Social class in Britain is not complicated.
You are what your parents, usually your father, are or were. It often revolves around occupation and level of education required to achieve it. Earnings generally don't come not it. Education is the primary social class marker from type of school up..The upper class are the exception to the rule.
Son or daughter of a man with an inherited title, upper class.
Son daughter of a man in an old established profession e.g. medicine , law, city banking or high finance, upper level civil service, clergy etc = middle class
Son or daughter of, manual tradesman or lower e.g. plumber, bus driver etc, working class.
Both MC and WC have 'levels'. Upper MC = old money, trust funds, public school education, Oxbridge or similar , established professions etc Lower MC = lower level professions, most teachers, allied health and senior nurses, mid ranking civil servants etc. Upper WC = tradesmen, hairdressers, staff nurses/auxiliaries, etc. Lower WC = unskilled, minimum wage, transient work, welfare.