Big, big, big thank you to @Kit Car Electronics, @Trevturtle, @bunje and the others who helped out with suggestions in the thread (and past threads).
NEVER BELIEVE WIRING COLOURS!!!!
Using Mike's drawn diagram and a clear head after a troublesome night's sleep I got back into the garage this morning. Measured for continuity between brown at connector and brown at relays. Yes, they are one and the same. Then did the same for the green one at the connector and the green one at the relay. Yes, they are also the same... however, the green at the connector is NOT the ignition 12V, it is the bleeding fuel pump output! So swapped the green and white wires around and sure enough, on turning the ignition, the fuel pump whirs up and shuts after 3 secs. Pressed the starter button and after cranking a bit...
IT LIVES!!!!
Lots of smoke coming of the exhaust wrap (knew this was going to happen, just needs to be burned off), and the idle is racing up and down between 800 and 1200, so I'm going to look at the throttle cable and ensure it opens the throttle bodies slightly. Also would like to make sure both sides are equally open, so some reading to do on balancing them and seeing if I can find one of those synchrometer things to see what the air flow is into the bodies.
Looks like I'll be taxing the car tonight after all