Could be absolutely anything
the tdci engines are pure cack to be honest
i used to work as a fitter at 1 of the midlands top diesel specialists

the fuel pumps are problematic as is the injectors
but if theres no fault codes its a little strange

if i was you id give it a sniff of easy start to make sure it will run & its not something drastic

Has anyone else had a play about with it ?

Can you see all the dynamic parameters on the computer
your plugging it into ?
So you can check for sensors working etc

they can be a absolute twat to bleed up after the fuel pipes have been took off