Checked and double-checked what the RGS does, and how/when it does it. Grabbed a momentary push button switch and some twin-core from my spares box. Mounted the switch in the dash and ran the wire back to the RGS connector. Twisted and taped everything together and cable-tied the heck out of it.
Tested ... drop into a gear, turn the park brake off, jab the push button until the Auto Park light goes out, and away we go. Stop, flick the Park brake on as normal and everything works as it should.
I just have to remember to jab the push button before trying to drive away from a parking spot; but then, I won't be able to move until I do