Ok....
Been doing some Internet searching from across the pond, this problem seems mainly to affect 2009/2010 370z.
Loads of issues in USA. There was mentions of hearing the wheel lock whir in and out when the cars ignition is turned off/ on, but when switched off it won't fire until the door is opened. Anyway, I never got the whirring noise, so it must have been jammed in the unlock position fortunately.
I turned the wheel with the ignition off and door closed to its full turning circle both ways, in one direction I heard a positive clunk and the wheel was locked, pressed the start button and heard the whir of the locking pin being pulled out, wheel now free to turn, so I am hoping that was the issue..........