I accidentally found an easy way of removing/replacing the top front arm.
While trying to remove the right hand one to remove and replace the cone I could not push the pivot pin forward enough to get it out of the arm.
The clutch housing, brake pressure switch were in the way.
While pondering, I heard a clunk under the car and the top arm had extracted itself onto the garage floor.
Mmmmmmmm, if it comes out that way it must be able to go back in the same way.
This is what your mini looks like without the arm.
Set up the arm like this with all the bearings and seals
Pick up the arm and feed the shaft through the front hole of the subframe.
Push it in till the seal starts to go into the hole as well.
Like this
Now you can rotate it to push the back of the arm in and centre the front of it on the hole.
It should now look like this.
Push the pin back and fit the rear washer and nut. Fit the big washer on the front, locating plate, washer and nut.
Tighten up, and it's done.
Wish I realised this when I did the other side last week
Removal should be the reverse of this.