So in the wash up, it seems that the manuals differ by firmware version quite greatly, but seem to have consistent instructions on pairing procedures. They are all rubbish, only because of the syntax and sentence structure makes it confusing. I've had to talk with Sena on a few occasions, trialled a lot of combinations but I've found one that seems to be the most stable.
The Nav V will try to take over everything, so you can do two things with the Nav V, either pair THROUGH it, to the headset or pair in PARALLELL to it, direct to the phone.
The difference is that when paired through the Nav, you have full HUD control, but lose Siri capability, and the reverse with the parallel setup.
I've chosen to pair in parallel as I prefer Siri capability over the HUD. Though I may change my mind
I get some Bluetooth interference when paired through the navigator which is not present when the headset is paired direct to the phone. Not sure why but I may do some more research. It could be a firmware problem.
I would suggest pairing the headset to the phone, then the phone to the Nav V. If you use the speakers on the bike or a separate Bluetooth transmitter (either BMW or some other transmitter) then go into the Bluetooth settings on the navigator and untick "media" in phone setting menu. Otherwise the navigator will try to hijack the whole operation, and on the RT that's a problem as the audio from the navigator is programmed to go out through the bike....
The SR10 on my bike is stand-alone and treated as a "plug-in module" which I only turn on when I want the UHF/ CB. As it is paired by phone selective pairing you can have everything else without it. I will soon be hardwiring the SR10 under the seat with a custom harness so only the radio is on the dash.
The SM10 (my audio feed) is wired into the line out of the 2012 model, and lives in my phone compartment after a small cutout was made in the foam and a wire port was drilled and sealed for it to live there. It is paired to the helmet via phone pairing. I'm still working on a switched power source that won't give any white noise.
Hope this makes sense? Feel free to ask any questions.