In the mean time...
I've read the manual (first time for everything!), and it says no problem with HDDs.
It needs to be formatted either FAT16 or FAT32, and a single partition.(or will only see the first partition etc)
The only warning that if the HDD comes with a AC adaptor, then that you are best using it. (as the USB socket may not have enough power)
I will let you know how i get on