Having looked at all the advice, I thought that I'd try the Western Digital, and if I didn't like it, I could always stick it back on Amazon marketplace. I've been held up by being sent a dud one.
It does everything that I want, very satisfactorily. For my money the only thing that would improve it would be to have shortcuts to your most used folders on the main menu and, perhaps, to be able to replace the screensaver with something more interesting, perhaps a slide show.