Glad to hear that you're mostly OK after your harrowing experience.
I am confused by part of your story though. You said, and I quote
" I'll apply a bit of brake and pull her back over - no such luck - with the engine shut down all I had was a lame , more like, non-existent brake"
Maybe the older servo brakes were different than on my 05/06 variety, but since only your engine died, shouldn't you still have had fully functioning servo brakes since your ignition was still on????
This makes me think that you definitely have an electrical issue possibly related to the ignition switch which shuts EVERYTHING down, including the servo brakes. Certainly doesn't sound like a mechanical issue at all.
05 BMW R1200RT
12 Suzuki Burgman 650 Executive
86 Kaw KLR250
05 BMW F650GS
06 BMW R1200GS