Okay so to give an update, and hopefully increase the chances of someone knowing whats wrong, i've done some more investigating and found the following;

When cranking there is initially no signal to the injectors, but once fault codes P0251 and P1211 appear the ECU starts to send a signal to the injectors. However, it still doesn't even cough.

If i disconnect the fuel metering valve (brown plug on back of pump) i get a signal to the injectors all the time i am cranking. However, it still doesn't even cough.

Live data of the rail pressure shows that when cranking with everything connected fuel pressure increases to around 500 bar, and when cranking with the metering valve disconnected this increases to 1200 bar. If i disconnect both the metering valve and the injectors the pressure increases to 1600 bar. Then as soon as i stop cranking the fuel pressure drops quickly to 8 bar and slowly from 8 bar to 4 bar.

Live data shows that engine speed during cranking is around 200 rpm.

Camshaft sensor has 12 volts between middle wire and right hand wire (as you look at the back of the plug) and 3 volts between the middle wire and the left hand wire when engine is still, which then fluctuates between 3 & 4 volts during cranking.

I performed an injector leak back test and found that each of the injectors has between 10ml and 20ml during cranking for around 1 minute. However, I'm unsure what leak back levels i should get when cranking with 4 good injectors.

Live data shows the mass fuel demand as 39mg when i start cranking and then this drops to 0mg as soon as the P0251 and P1211 codes appear.

FORScan says in the info for P1211 that the throttle position sensor is open circuit.

I have checked the live data of the accelerator position sensor and this is fine.