Gentlemen, the engine is running! The car was started a couple of hours ago and it drives ok.
The doner loom, ECU and chips were all from 2001 (not from 2003 as I was originally informed) and therefore fully compatiable with the dashloom of my Astra which is also from 2001.
The problem was something much more simple; the mechanic had swapped the fuel lines by mistake. So, no fuel was going into the fuel rail!!
I am so relieved that it was something as simple as that and not much more complex.
Next task: RDW and how do I register the new engine with them?