Accident damaged 2006 TD6 Range Rover won't start with key

I have a 2006 L322 TD6 Range Rover Vogue that was in an accident in January of this year. The vehicle had been damaged on the drivers side front and rear quarter panel. Work on the vehicle began in April after receiving the parts I required.

I have now completed the bodywork on the vehicle and am now in the process of rebuilding the vehicle. My problem is that the vehicle will now not start using the key. This vehicle had lay in the workshop for 3 months and the battery had drained.

When I went to start the vehicle to move it into the spray booth for painting it would not start with the key, however when I crossed the starter motor the vehicle fired up. Even with the vehicle running after crossing the starter the vehicle will not select any gears and crunches when trying to select gears. All fluids in the gearbox, engine and diffs are at the levels they should be.

Can anyone give me any ideas on what the problem may be and how it can be rectified.

Thanks