UPDATE !
I thought it would be good to post the latest for all
interested parties. Been trying to juggle looking at the van around work hence the slow update. I re installed the PCM this morning. I then cleaned up several grounds that were awful. Confident this was my issue I put it all back together, turned the key and .....
NOTHING!! :(
So I tried each sensor by unplugging individually but again no joy. So next I decided to have a proper look inside and underneath the engine fuse box. I noticed one of the cables by the moulded plug had a green powder on it. Knowing copper turns green when it oxidises gave me new hope. On closer inspection the cable was split and it was just the insulation holding it there. I traced the cable back to the fuse board (it was black and orange) and would you believe it was for the power up relay (R8) . Unfortunately the cable broke right at the moulded plug. So I cut back the loom slightly and crimped a plug in to the cable. I then ran a new cable from there in to the fuseboard and cut the black and orange cable from the relay. I then crimped in a plug there and connected. So effectively I've by passed the moulded plug and made my own .
Put it all back together and it's started! Hopefully this thread will prove useful in the future for others.
Many thanks for all the help from everyone who posted .