TD5 Won’t start, think electrical...

Hi,
Today was the day my Defender decided to die on me... my mechanical knowledge is nut and bolt based and sadly this isn’t a nut and bolt fix.
Car - Defender 110 TD5 2004
No prior issues but car won’t start. Drove to my destination fine, when I went to fire her up to get home it just turns over and doesn’t fire. On the way Idid hear what sounded like something fall off and hit the footwell, couldn’t see anything obvious on the road and was driving undertrees so assumed it was a branch - car continued to run fine.
Fuel pump does not run - I have tried wiring the fuel pump relay so that it would run which it did but the truck still won’t start. There is, as with all TD5’s, oil residue at the ECU so will clean that out tomorrow. Have also read that a flywheel sensor Issue will stop it from
Starting - perhaps what I heard fall off? Although I assume it would have cut out straight away.

Any suggestions or advice? Not looking forward to a new ecu and programming bill...
Cheers!

Try cleaning the earth under the drivers seat, near the ecu. Also check the 'big' fuses in the fuse box under the seat.

There is a fuel cut off switch located on the bulkhead at back of engine bay, these are activated when a collision occurs, but have been known to do so without impact. Try depressing the button on top to reset and see if it fires!