Well today I think we see a little improvement. I removed his food (going to be feeding him twice daily). He looked a little lost, and hungry (walking along the bars of the bottom of the cage looking at the tray below trying to access the dropped food!!). Anyway, we put a piece of apple through the bars in the cage (not holding it) and he came right over and took it...we of course did the holw "Good boy" thing. We repeated this a few times, until he was coming almost immediately...but if we approach he'll still back off.
He seems more interested when we approach the cage though...still moving away, but clearly looking to see what we've left. Right now I have a monkey nut through the bars next to me, I'm not holding it...just doing my thing on the PC. He's not approached me for it yet...but he's keen...and is well aware it's there.
Hopefully this will begin the process of him associating us with good things, instead of negative!