Imagine if in 1987, instead of a Tory landslide, there had been a hung parliament. What would have happened? The conventional wisdom is that Margaret Thatcher, the Iron Lady, was a conviction politician and unable to compromise. That's the appearance she gave and very well it served her too. But in reality she was a pragmatist, especially when it came to important negotiations. Her firm stance in advance of many EU negotiations meant that she exacted many more concessions than she might otherwise have done, but in the end she knew she had to do a deal.
I have little doubt that in 1987 she would have sought a coalition withe SDP/Liberal Alliance if the parliamentary arithmetic had meant that was the only way to continue in government. What I am les sure about is her ability to have pulled it off. Certainly David Owen would have been up for it, but I doubt whether David Steel could have persuaded his Liberal Party, even if he had wanted to.
If Margaret Thatcher had been Conservative Party leader at the 2010 election I have little doubt she would have done exactly what David Cameron did.