Thanks Jofm!
Fortunately, I managed to get it working... Because it was a few years ago when I last installed it, I couldn't remember the reset procedure...
You hold the white button on the rear in for 5 seconds whilst powering. The HP software then magically 'saw' the printer and I now have a working printer.
I had a quick nap after posting and the reset procedure came to me. I guess I should've had the nap before posting here...
