Good news - sort of. Actually no - good news.
I've just gone and tried again (clearly I am agitated enough to go out and try again at 10pm at night) but it had good 3 hour downtime with vehicle turned off.
It immediately paired to the iPad.
The iPad was still in the child's room no where near the Overland.
Ok, so manually disconnected the iPad through the screen and manually connected the phone also through the screen.
Connected successfully, phone book all good - waited for 2 odd minutes - and... Booya! - Messaging back.
Not sure what's going on. Why did it connect to the iPad first when it has never ever done that before and more to the point, the iPad is nowhere in range of the vehicle.
I have a feeling it needs to settle down for the next day or two - had a too hard a day at the dealership maybe...
Anyway, I'm going to relax now and know that in a day or so, all will be back to normal. Positive thinking...