And after finding a message on screen 'SIM registration failed) or similar, I'm back to where I was before, albeit in R&D mode.

The odd thing is that if i switch the lock button, or press any of the cam butons, open the shutter etc, the keypad flickers (which it does in R&D mode to indicate activity) so there's there's life in there.. Weird... Don't really want to have to reflash AGAIN, but it looks like I'm going to have to..