OK. I played around a bit tonight.
I took an old 4 port USB hub I had lying around, and replaced the input usb wire with a power socket. Then I used a 5V 2.5A power supply and connect it to the new power socket. My Galaxy S charged (saying it is connected to KIES), but not my Motorola Defy, or my iPad3. After lots of head scratching, I turned to my friend Google to discover that the data pins of the output USB connectors must be shorted. Now all my devices charge nicely from the hub.
One last problem is that there is some heat build up within the hub. I am most likely going to build the whole thing from scratch, to ensure there are no heat generating components inside and to get a nice looking case.
But for now it will do