Thanks for the replies and sorry I haven't come back sooner.
I checked wires that were disturbed during the head removal/refit process and found the crank sensor wires broken, and in the injector plug on the end of the main engine harness, the plastic mouldings that keep the pin-sockets in position had broken away allowing all the sockets to be out of line when refitting. Suspecting that the integrity of the rest of the loom was not great in the long term, I replaced the complete engine management loom at a cost of £380 the best price I could find, from island 4x4. Also replaced the crank sensor whilst access was good.
Engine started almost immediately- perhaps the best ever restart after disturbing the injectors or anything to do with the fuel system, on my particular vehicle, which is normally a real cow to bleed through. It definitely helps have a full tank when bleeding a td5.
Shaun