They can be answered two ways:

What do we Zoners do, here? That's easy: no matter which of the two options you present occurs, some will gloat, some will waffle, some will go quiet for a while, and some won't care.

What do "we", supporters of a free democratic world society do?

If weapons are found, good - that, at least, will provide vindication for one of three or four stated reasons for invading Iraq. If weapons are not found, the question remains, "What led the decision makers to believe they would be?"

If a Nixonian conspiracy is uncovered, the participants ought to be, where applicable, removed from office by the due process contained in the Constitution (and whatever analogous procedure obtains in the UK), and/or prosecuted without benefit of pardon by the succeeding Chief Executive.

Here's a corollary question: What do we do if (whether or not weapons are found) the coalition's "aftermath teams" fail to foster stable democracies in Afghanistan and Iraq, so that the situations there revert to pre-invasion tyranny, only with new faces?

I think that answer's easy, too: elect different leaders, next chance we get.