James...
The handle release on mine doesn't work very well, if you try and push it around in the "locked" upright position it stays in that position for a few seconds and then drops down to operating position, all Juniors do this, because the 60's and 70's ones are getting on for 30-40 years and the metal on metal handle release has just worn from constantly being pressed and tugged on over the years.
You may be able to get a "new one" from a vacuum shop as they usually sell the refurbished Juniors but I am not certain on that, plus it will be bright white and not the yellowy creamy colour of the U1012.
If you need to get to the motor, there are four screws that need to be taken out. Fist take out the two screws that hold on the black bottom cover, then you will need a VERY long Phillips head screw driver (if you don't have an extra long one it just won't work, no innuendo!) and then unscrew those four screws, the motor will just lift out.
When you have the motor out (from memory) you should just be able to unscrew three long flat head screws that have a bolt on the back, the motor casing should start to break into two when the screws are out, just remember that the screw and bolt that goes in at the rear of the motor is slightly longer than the other two, I think. The carbon brushes are held in by two little plates and there are two little flat head screws that hold them down in place, when those little screws are out the carbons will just spring right out.
Hope this helps you,
Alex.