Optima accenta g3 system locked, panel shut down?

I was removing a PIR sensor from the wall when decorating and set the tamper off a few times whilst removing/refitting the cover. The system has decided to go into a shutdown mode where none of the sensors (3 PIRs plus window sensors) seem to be working - leds do not light. The panel shows the day mode light and still responds to the buttons etc. The manual says that by default there are 3 automatic re-arms before the panel is shut down so I think this is what has happened.
Does anyone know how to bring the system back to life? I have tried pressing reset several times and entering Engineers mode and doing the same. Any suggestions much appreciated.