Personally I think best thing to do is read different viewpoints on her merits and failures.
http://www.economist.com/news/briefing/21576081-margaret-thatcher-britains-prime-minister-1979-1990-died-april-8th-age - Mentions how she got 'lucky' with being able to push through the reforms she felt the country needed i.e Falklands War (her popularity soared afterwards) and North Sea oil revenues (16% of GDP). A very pro-Thatcher article.
http://williambowles.info/2013/04/12/the-ironic-lady-margaret-thatcher-supposed-champion-of-freedom-and-democracy-and-her-dictator-friends-by-nima-shirazi/ - Maggie the lover of freedom and democracy...when it suited her. She was friends with a lot of dictators.
http://news.liveandinvestoverseas.com/Politics/prime-minister-margaret-thatcher-the-pros-and-cons.html
