Indeed. If Thatcher can bring herself to attend Heath's, then the least Blair could do is to attend the funeral of somebody who, whatever your views on his politics, was the formost parliamentarian of his generation and a major figure within the Labour Party.
Blair sent a representative. Current heads of state should not be expected to attend most funerals.
Especially ones with major domestic terrorism crises stemming from a 5th column, and an ongoing state of war. In the USA it's the job of the vice president, whose motto is "you die, we fly".
Why would anyone try to compare the Lady with Blair? She has always shown poise, bearing, style and manners. Enough said.....