I would put Thatcher's roots as Working-Class. Her old man was a corner-shopkeeper in a small market town - hardly qualifies as the equal of, say, a doctor or lawyer? More the equivalent of a shop-floor foreman in industry. Yep, definitely nowhere near Middle-Class, obviously Working-Class.

And her lifelong rage at her own lowly beginnings was what drove her loathing for, and viciousness against, those who shared her roots. She hated them because she hated herself for her own "common-ness" (her speech, of course, betrayed her - she would no doubt have had a natural Lincolnshire accent, which she tried to disguise by metaphorically inserting a pound of plums in her mouth. Never quite came off - her posh-talk always sounded affected and 'put on'. Another betrayal of her roots).

IMHO. YMMV.