Hi Dom,
Hopefully i can be of some help even though James's advice on here has helped me hugely, i know how frustrating it is when all you want it to do is fire up!
Here is a list of all the connections i have made, bear in mind that these are all new connections and the only existing connections i have used are the cables for starter so the ignition turns the V8 over. I have also got 3 really good earth straps one at the front right hand side if your looking at the engine face on it goes from block to tab on the chassis, one at the rear from head earth bolt to bulkhead and another from head bolt to chassis.
At the multiplug i have the following;
Brown Wire - This goes to + on battery which is fused as a permanent live
White / Grey - This goes to switched ignition tab on ignition barrel
White / Purple - This goes to + on fuel pump, the neg on fuel pump goes to chassis
Black Wires x 2 - These go the right hand rear earth bolt if you are looking at the engine from the front
I have then put in another wire from switched ignition tab to + on Coil. Also on coil should be 2 wires for amplifier and the one that uses the same conduit as the mass airflow to say the engine is turning.
It was this one that caused me all the pain and the earth ones that are black once i had connected these the whole thing just came to life and this was after i had replaced (unnesserialy) boith main and fuel pump relays.
The relays should both click when you turn on the ignition, my fuel pump primes then approx 4 secs later the fuel pump relay clicks off again, it should also make the fuel pump run continuosly when cranking.
Although as you have said it will run with the fuel pump switched to a permanent live circuit its just not very safe.
To make it easy i just slaved everything in first and labelled what i had to stop confusion.
Take your ignition barrel out so its hanging and you have easy access to connections then slave the above cables in and see how you get on.
As i say the main thing was the earth cables so i went a bit ott and now its fine.
Ill try and post pictures later.
Josh