Hadn't seen anything further and just wondered. Were you able to get it working?
apologies for not reporting back - it did turn out to be cable related.
I havent tested it since, but I think the USB cable was screwed - I think it may have been put in one of the other sockets (network or fax). The problem seems to have been complicated by the fact it was a long (3m, - 10 feet or so) cable. I replaced that with a shorter usb cable attatched to an extension. This had worked previously (and also works since) but the printer was not recognised with it. I rang HP and they were saying they'd replace the printer (they didnt seem surprised) but they guy did ask me to try with a shorter cable first. They got me to do a reset on the printer as well - it's possible that helped too. When I moved the printer nearer and used a shorter cable it worked.
I really should have fully checked out the cable possibilities before anything else, but I didnt - live n learn...
So, thanks to all for your help!