IMHO, we do not need to go rummaging around Iraq to prove this; we have a reasonably good intelligence service, and they certainly have all the documentation anyone could need. There is a reason why this has not come out before now, and there is a reason why it is starting to come out now.
Because Bush & Blair on the one hand and Chirac and Schroder on the other have climbed so far out on their respective and opposite limbs, I see no possible way at this point to have a "win-win" outcome. Thus I also see no possible way that the French can cast their veto of the 2nd resolution and not be discredited and humiliated in public. Nor do I see any possible way that France, Germany, and Belgium can continue to be "allies" of the US & UK in any meaningful sense at all. The amazing thing will be if we even continue to have diplomatic relations with them after this is all over.