cardibach
I don't see it as strength of character. I see it as arrogant, pig headed stubbornness. Not good qualities. True strength of character requires doing what is right, not convenient (and before you suggest that is what she did, think about her support of apartheid because of her husband's business interests) and in admitting when you are working as well as taking advice form those who know better.
Firstly, let's deal with the SA smear. The world in the 1980s was more complicated than you acknowledge. There was a global struggle for power taking place. MT backed the SA government because it was a bulwark against Communism, just as she backed Iain Smith and Pinochet. Mugabe and Mandela were both Marxists, the Soviets fomented rebellion in Africa in order to destabilise pro-Western governments just as the Americans and British did against pro-Soviet governments. It wasn't about 'business interests', it was about the Cold War and the threat of communism.
Now you can argue that she shouldn't have done it, but at least argue honestly that you think she should have allowed SA to be run by a Soviet puppet government.
Secondly, stubbornness is essential in a leader. If you're PM, your cabinet consists of about fifteen people who all have massive egos and all think they're better than you and should be doing your job. If you're going to actually get anything done at all, you have to be prepared to be stubborn and ruthless. If you don't, we end up with a Cameron or a Heath or Brown government, with dreadful decisions made and then cancelled, and drift and a lack of focus on the needs of the country.
Thatcher thought she knew better than anyone else about everything and would not take advice or listen to others. David Mellor on This Morning talked about her putting Cabinet ministers down - he said it as though it were a good thing. It isn't. Nobody can run a country alone.
This simply isn't the case as anyone who has read either her biography or her autobiographies can attest. She wanted people to fight their corner. The most memorable incident I can think of off the top of my head was a minister who disagreed with Thatcher on a point of policy. There was a forthright exchange of views. The minister left. The next morning the PM summoned him and said "I have been thinking over what you said and you are right."
She was perfectly capable of taking advice and listening to others.