I think its standard with the premium pack plus on the new cars but a option on the old one even with a premium pack it was only £335 as a option.Unfortunately my M4 doesn't have the CBBs and I think the brakes are probably the poorest part of the car for me which is why I was interested in a c63 with them.
I've looked at the Zenith one and if it had carbon fibre interior trim it would have been pretty much my perfect spec. The 360 camera is also a must for me as I have the 'surround view' on my M4 as well as HUD and wouldn't ever want to own a car without both of these now. I didn't realise the 360 camera was such a low cost option, I thought you could only get it as part of the premium plus pack (think that's the case with the facelift anyway) as ideally I wouldn't want a sunroof from the premium plus but need the 360 camera.
I agree with you about the HUD & 360 cam i wouldn't want a car without them on it, also night pack is a good option to have.
All the best with your search.