Hi Hugh,
If you're not already a member, have a search through this forum.
http://www.thed2boysclub.co.uk/ It's soley for the D2.
One question - when it stops, have you tried the purge cycle (Ign on and pump throttle pedal 5 times to prime system) If this works it's air in the system. As you've already changed the pump and seals (with genuine I hope!) then check the fuel filter housing as this can get porous, and also the air bleed valve on the top of the housing. (I think it's the rear outer one)
HTYH,
Griff