Blair doesn't get a free pass because Saddam was an evil man and he went with good intentions. There are lots of murderous dictators that I don't like (Assad, Kim Jong Un, Putin, the Myanmar Junta) but if toppling them causes more chaos and far more deaths than would otherwise have been caused had we never gone then it's always a bad idea. Blair, like all leaders, will be judged with hindsight. And the fact is, he spent billions on a legally dubious war that undermined and alienated the international community, inspiring hate against Britain and the West, and almost certainly left Iraq, Syria and the world in a much worse place.
It's not about Thatcher adoring Blair, it's about Blair adoring Thatcher (which he constantly mentions), leading to crippling and failed privatisation experiments that's bleeding the country dry and will continue to do so for another 30 years until these contracts come to their conclusion.
That's not hard. We had a booming global economy (not because of him in the same way that the crash wasn't because of him or Brown) and he still borrowed us into debt up to our eyeballs. When you're spending all that money, all of the outcomes on your outdated list (more nurses, higher welfare, more teachers etc) will be achieved. Abandon all sense of budgetary responsibility and living standards will go through the roof. The problem is, it's short-termist and burdens future generations with enormous debt and when the economy isn't doing so well and the interest needs to be paid down, people start to suffer.
Immigration is all well and good (and obviously immigration will lead to total economic growth) but they need houses to live in and there needs to be a concomitant, long-term rise in living standards for all for the policy to be popular. The houses never got built and his policy (and absent of policy) led to an enormous housing crisis that's stoked anti-immigrant sentiment which has culminated in Brexit.
Sorry I said 42 days - that was Brown. Blair tried to lock people up for 90 days without trial, leading the House of Lords to declare the law incompatible with the Human Rights Act.