I need a ruling from our (self-appointed) arbiter of all things fashionable. Tony Blair is now sporting a mullet ('business at the front, party at the back'). I think he looks very seedy, like an elderly porno director.

As usual, you nattering twits have it all wrong; that is not a mullet. There is no appreciable difference between the length in front or on the sides and the back. (Contrary to popular belief, it is the difference between the side hair, above the ears, and the back which defines a mullet, not the top.) It just looks like his normal awful hair grown out.
I agree that he looks seedy but he has always looked seedy because, like so many of you, he persists with a silly center part (or in earlier days more of a target where he just aims the blow-dryer) well past the point where his poor face has curdled. Center parts are for the young and beautiful because they emphasize symmetry and look nauseatingly absurd atop the ravages of age. For years he has made me sick.
I am not opposed to a silver leonine mane when nature affords that distinction but it must be done boldly and with style. Here it looks lank like he just slept with it in a pillowcase. Do you have hairdressers over there? A dry shampoo and the merest touch of pomade or putty would do wonders; he still has enough volume to do things with.
And I did not appoint myself so much as grasp, with a firm and manly yet gentle grip, the wildly swinging tiller of a poor vessel slewing perilously upon the billows with no one moving to restore control, because talking about fashion stuff is gay and any man who makes the slightest effort to redeem his dignity must be secretly sampling the spit-soaked swamp of perdition.