Calum wrote a very good report of how to change the hub, if you search for "Hub and Sprocket Change" you should be able to find it.
In the same post I added a some info of how I modified the existing hub to achieve the same results by machining 5mm off of the wheel flange of the hub. The flange was reduced from 20 to 15mm. thickness. Maybe not as desirable as a new hub but it only cost me £30. I also fitted the new steel pulley a few weeks later.
The belt now runs in the middle of the pulley with about 3mm clearance between belt and tyre. I have done at least 1000 miles since the mod with no problems, it drives better and is a lot quieter.
