Quick update :
Spent an hour or so this evening sorting out some of the wiring. I've run the 7 core cable from the ecu to the switch next to the gearlever.
I took the plunge and snipped the wires Stated the car up and took it for a drive, D was overdrive as per the BGB specs when the solenoids are disconnected, so it appears those are the correct wires. The car didn't throw any fault lights which is a bonus.
I've soldered the wires onto the switch and i'll give it a test run tomorrow to see if it works ok to disconnect the solenoids. Hopefully i'm going to lash the box in there later this week if I get chance.
End of this week i'm off to Hong Kong for 3 weeks with work so i'd like to try and get something running before then!