Just wanted to add an update to bring this thread to a close for anyone determined enought to have read this far
Computerwiz12890 had the excellent idea to run Knoppix OS from CD. This allowed us to check whether the problem was Windows related. Two of the ports worked, four didn't. So now I know that there is a hardware issue - the PSU is a suspect at this stage, but it could be the motherboard USB hubs themselves.
In device manager (back in windows) I uninstalled everything USB and on starting up the same two ports as in the Knoppix test came back to life.
I'm happy to live with 2 out of 6 for now.
Thanks Computerwiz12890, Jack123 and all others who helped in this.