IT RUNS!!!
Faults were:
1. Had to swap diagnostic pin in car's socket from Pin 11 to Pin 6. This was accomplished by pulling the centre white insert out of the socket and swapping the terminal across (other space was blank).
2. Key "forgotten" but with dialogue through the revised pinout, I could reprogram the (gasp!) one and only key.
3. Main power feed to tachymetric relay was not working - still unsure why. We jumped it and BAM! off she went.
Now needs exhaust, air filter, hooking in of lambda heater feed, and tidying up. In troubleshooting, we buzzed out every sensor except the knock and MAP (both near inaccessible). All splices good, all crosses except the above were fine. So my wiring skills aren't too shabby, just my current-finding ones.
Also note that with the Xantia CPH (body computer) you may need to short out the front door latch contact wires so it doesn't log permanent faults of both front doors open...
I am a happy bunny today. There's a minor glitch with the dash temperature sender wire but I'll sort it (Xantia feed has two wires, Berlingo only wants one).