Great article, James. You're the bravest man making a new bellows yourself and it looks so nice.
2 points to discuss:
I love the Prontor-S shutter, it is reliable and easy to work on. According to Jurgen Kreckel (again and who is a very kind man) the Compur shutters are 8 times more often unrepairably broken. Did you open it from behind? I would never open the shutter from behind if not needed. When all lens elements are dismantled, it's easy to open the shutter from the front and clean it. No hassle with the aperture blades, they all stay in position. No loose parts fly away. Let sit the opened shutter for an hour in the cleaning bath, I use isopropanol, it's much less agressive than lighter fluid. Cock and fire the wet shutter and move the aperture, it will clean most probably everything. Repeat the process if neccessary. When the shutter is again well dried, some tiny drops of machine oil may be necessary applied at the axle of some gears. Wipe off immediately any excess. Cock and fire the shutter with the speed ring held in position to see if everything works. Before re-mounting put a tiny wiff of oil on the shutter disk and speed ring for smooth handling.
If you have a well collimated lens it's not neccessary to recollimate it again. Mark the infinity position of the front lens after removing the focusing ring and mark the position of the lens when it comes off. Mount it at the same thread position and screw it in completely, then screw out until the mark for infinity matches. Infinity is usually a small fraction of a turn back from the completely screwed in position. The second and the rear lens element are simply screwed in as far as they go. Of course after dismantling the film mask and replacing the bellows a new collimation is needed, but if you only want to clean the shutter and the glasses it's not necessary if the lens had a good infinity focus before.
Good luck with your fine Isolette, she could survive all of us.