Well, I finished my fan install today. After a lot of reading through the workshop manual I came up with the circuit below.
On the left the relay with the flashing LED is optional. I installed it so I wouldn't forget to turn the fan back on. Because I used a 12 volt supply that is always on it also doubles as an anti-theft deterrent.
With the switch, up is auto, centre is off and down is on.
To wire in the relay, find the dark blue with a pink stripe, cut it and put you relay here. Connect the dark blue/pink wire closest to the existing relay to the new relay. The other connection on the new relay, run the wire into the switch on the dash and back to the dark blue/pink wire that runs to the PCM as per diagram.