power steering

Back to the saga of my daughters 05 Micra. The powersteering on my daughters 05 Mica failed again after the fitting of (2nd) recon unit. The local garage sent it back to the suppliers in Tamworth, who"repaired" & returned it. The garage refitted it (after five weeks) & my daughter drove it home. However the NATS light was on (again). As she was going on holiday I offered to reset the lamp as i had done the last time. When trying to start it, the car is dead, the radio goes off, but the dashboard lamps stay on. Any suggestions would be welcome. We don't want to go back to the garage because they keep it fo weeks.
Update. Battery disconnected for 24 hours. Replacement battery in key (although tested ok) Tried this morning. Worked ok, no warning lights, just like last time. I'm not posting this as a sure fire cure, but may be worth trying if you have the same problem.