Using a multimeter check at the connector to the mirror at the non working side when the button is pressed.
Were the orange and orange striped wire definitely at the car side of the door loom connectors, as that's where it's missing from lower spec cars?
The Driver's side will always work as the wiring at that side is complete in the driver's side door loom
If it's not working on the Passenger side it's definitely either a connection issue at one of the door loom connectors, the connection to that mirror or missing wiring.
It's a just a switched loop that runs from the Driver's switch pack to the mirror and back again
Russ