Oh Crap, I forgot to update what happened.
My son pulled the alternator out from underneath (I think it may have to go upwards a bit first) - 30 mins.
Pulled the brushes out - 10 mins - took them to the Toyota dealer who did all the partnumber work.
Next day new brushes - installed into the alternator - 10 mins - then 30 mins fiddling to replace the alternator,
which was fiddly trying to line the holes up etc, 2 man job had it quickly sorted. All up cost $15.
My son seems to be winning at each of the tasks I give him.
He just pulled the driver's seat out and got stuck into reconditioning the leather - looks great now - all the white wear marks are blacked again.