Thanks for the info, seems that the problem is a combination of things, the auto disconnect after 2hrs on BTopenworld and the fact that the drivers they supply for the Alcatel usb modem are downlevel.
Well thats what BT say, all I can do is try out their suggested resolution !
Power (certainly) and bandwith (possibly) on the hub could be Red herrings.
Ill be convinced when the drivers fix the problem.