"Do you think Bush wold have gone into Iraq without Blair? Britain was the only ally of any consequence in the "coalition", but I think GW would have gone it alone if necessary."

I think Bush would gone into Iraq without Blair- but Blair certainly helped. And I think Blair *probably* wouldn't have been Prime Minister of UK for very long if he didn't. One should keep in mind that it can be argued that the reason we are in Iraq now, is because of UK leadership. [I refer you to Gulf war I.] And because of UK involvement in this issue starting with Gulf War I, The Conservative Party could have used this issue to endlessly bash the Labor Party. Example, presently the Dems are faced with problem of the general public NOT trusting them in matters of foriegn affairs. The Labor Party could have got this same stigma- Blair and Blair alone, saved his party from making that mistake. Also I think if UK had made this decision, then they would have probably approached as the Canadians did- support Afghanistan operations instead. So it could have been that in the effort of the entire "war on terror", UK could used more miltary forces than they are presently- and more UK soldiers could be dead, but their efforts could be more in Afghanistan. It's also a complicated issue, because without UK involvement with Iraq, US probably would have invaded Iraq quickier than it did or not invaded at all- Saddam wouldn't have trusted France's assurance that the US wasn't going to invade instead he would focused his intention exclusively upon the intent of what America would do [and that was pretty obvious and clear cut].

As far as Brits being only ally:
The most important allies were Kuwait and Turkey- without one of these two it would have been very difficult to invade Iraq. Had we had both Turkey and Kuwait being supportive of using their terrorities to base the operations, the war would have turn out differently. As we know Turkey failed to get the super majority required to support this. And of course Kuwait supported it. Other allies key to this were Jordan, Egypt, Saudi Arabia. Of course, politically speaking Israel wasn't much help, but it was helpful as it could be and certainly an ally [and probably more than is currently known in public {in case you didn't know it- Arabs in general hate Israel- blaming Israel for *EVERYTHING* that goes wrong in their world}].
This leaves two countries in region: Iran and Syria. Iran declared before the war that it was offically Neutral. And Syria made it clear that it was supportive of America's effort on War of Terror and didn't take position being a very loyal ally of Iraq despite it's close political and economic ties. Basically, all countries other than Cuba and N Korea weren't very supportive of Iraq. Lots of countries took position of "war is bad" but this about same as position that "shit stinks".
Another key ally was Australia and like the UK it's prime ministry was re-elected [unlike Canada's leadership]. Japan the world's second largest economic power was also an ally.