Just read the thread and the whole issue is whether it was actually an optional extra or not, as the Manufacturer had updated the specification to include your digital display as standard.
If the car also came with the other updated spec, then that would have told you that the car was just a standard order with the updated speck now including your digital dash display, which could no longer be charged as an optional extra. As such I do not consider that it would have been an issue that did not involve Motability as you were no longer being charged for an optional extra, you were merely being charged wrongly for a standard model upgrade in speck, which would be an issue for Motability. Glad it was rightly all sorted out, enjoy your new car.