Okay, I gave it a go for around 3 hours and had varying results - I still think I need a few pointers...
I noticed that the solution did 'foam' a bit more after an hour or so of being mixed - maybe I didn't dissolve the Oxy correctly?
I also tried it on an old floppy front-panel, which worked well and an Amiga 4000 spacebar, with light yellowing. Both were 80% back to original color after 2.5 hours...
The Amiga 3000 mouse, however looks a bit of a mess...

The flash and some contrast enhancement make it look a lot worse than it actually is!
The main issue seems to be the whitish patches on the mouse-buttons. The body of the mouse is also slightly 'streaky'. I did apply the mixture (which was quite thick and 'creamy') pretty liberally and put plenty on. I didn't make any real effort to make it a thin or even coat.
Questions now:
1: Can I fix the whitish spots with another proper full-time application tomorrow?
2: How thick/thinly should I apply the mixture?
Cheers,
Mike.