As there, apparently, seems to be evidence of Saddam providing succour to Bin Laden, and given that a war in Iraq is merely an extension of the war against terror, isn't that a valid reason to disarm Iraq and block it's financial networks from giving Al Qaeda anymore money?

Where exactly is this evidence? Many countries around the world have terrorist cells. It doesn't mean that nation supports terrorrism. Take the IRA, for example. At one time in the UK, anyone with an Irish accent was treated with suspicion.

I have just watched Colin Powell's speech at the security council in New York. He has suddenly come up with all this evidence against Iraq...and has known about this for some time. How come that this 'evidence' wasn't made available to the UN weapons inspectors in November? How come nobody is calling the US (or any other power, for that matter) to account for their weapons of mass destruction? When did Saddam suddenly become such a threat again?

Never compare yourself to others - they're more screwed up than you think.