Researching this problem I came up with this

CAUTION: If the power fold mirrors are operated
consecutively more than three times, then they
will cease to function for a period of one minute.
This is to prevent damage to the power fold
mirror motors.

My mirrors wouldn't fold, but an hour later when I came back to pick the car up out of the car park, they did.

So if your mirrors won't fold, and you keep trying, they really won't fold, by design !

PS they are getting a bit intermittent, but I can hear a relay clicking, so I guess its the relay contacts?