Range rover sport 3.6TDV8, cranking but no start

Hi, I have a 2007 RRS 3.6tdv8 that I've just fitted new turbos to, not easy but achieved with body on. Once all refitted the car fired up first time straight away and I ran it for 30 secs just to get oil pumped around, then rechecked and topped up oil to correct level, started car again and ran it for another few minutes just to check for leaks and allow coolant to start going round, then started car again and ran it for a further 15mins on drive getting it up to temp, occassionally increasing revs to approx. 2k rpm and bleed coolant system, everything ran well, sounded good, no smoke from exhaust, no knocking or any funny noises and heating system was starting to blow hot air. Stopped engine for about an hour before taking car out for test run, went to restart car, it started and died in a few seconds and now fails to restart, just cranks over and over.
Battery is fully charged, brand new LR fuel filter, have bleed through approx. 1 pint of fuel and looks ok and low pressure pump seems to be working, there are no fault codes coming up (OBD2 reader) but still won't start. My next thoughts are fuel pressure sensor and crank position sensor, is there any way to test these 2 or any other suggestion, also is there a way to check the high pressure fuel pump?

From what I read, the crank sensor is a gearbox off job, is this correct? and how is the high pressure pump fitted? if it is chain driven from engine is this an engine out job or is there a drive key way that allows pump to be removed?

Thanks in advance for any help

Best to ask technical questions in the range rover tech section. More rr owners will see it and reply.