It' been a while but eventually got round to doing a bit more investigating on the disco. I tested the fuel pressure as suggested and got a reading of 4 bar but I thought I would swap over the pump just to rule it out. I took out the fuel pump and got hold of another second had pump (vdo). At the same time I replaced the filter head and changed the valves inside too. Purged the fuel system she started with no problem, So took it for a spin. The replacement pump however was very noisy so wasn't sure how long it would last.
The misfire however seemed to disappear! Great so i thought .
About 5 mins later she started spluttering then cut out and refused to start . Managed to tow it home and set about re-fitting the original pump back in. She now refuses to start. I have no fuel pressure at all , I have removed the feed pipe to the fuel press reg and bugger all is coming out ! Tried the purge cycle and no amount of purging produces any fuel to the engine ! I have a quarter of a tank of diesel in which I would have thought was enough to get her going. I have also tried a new pump , checked and swapped relays, fuses,power supply etc. Please help before I torch this car !