"I believe the last Labour (sic) government was elected by about 13% of those eligible to vote."

It was nearer 21.5%. Thatcher's wins ranged from 30% to 33%. Blair's first victory was early 30s too. I think that it is pretty clear that Thatcher never received support from a majority of the British people though which was the point being made. Whether you look at those eligible to vote or those who actually voted that point is true! Likewise she polarised opinion more than had happened before certainly for a while. So she may have been extremely popular with some but she was extremely unpopular with others. Somebody said that Conservatives were quieter too. I don't think that is so! People who are more politicised tend to be more vocal whatever party they support.