Been thinking about the OP's problem, which started after a refuel. Something is inhibiting starting, but not the immobiliser as the engine cranks over. I have the handbook for the 2.2tdci and there is a paragraph in there regarding running out of fuel (assuming the 2.4 has the same characteristics). If the fuel level falls below a minimum level the engine runs at reduced power, followed by the engine stopping. After refuelling it has to be restarted with the following procedure;
1. With the brake pedal depressed, turn and hold the engine start key and crank the engine for 5 seconds.
2. Release the key.
3. With the brake pedal still depressed, turn the key and crank the engine. The engine should start within approximately 5 seconds.
If the engine does not start, pause for 10 seconds and repeat. Do not crank for more than 30 seconds or damage to the fuel pump may occur.
A long shot but worth a try?
Another item to look at is the Overide Inertia Switch located on the bulkhead, which might have been activated and may need resetting, or its fuse might need replacing. (This cuts off the fuel supply (via the ECU) in the event of a collision). Again, a long shot but worth checking.