A further update... I believe I have possibly found the cause. While driving today I reached over to the passenger side where the noise is coming from. Our of curiosity I pressed the roof lining for the rear shell which halved the amount of noise. I then put pressure on the braided cable that is attached to the roof mechanism (the part you can see from the cabin, where the square of roof lining is missing) and this did the same. I then pushed heavily on the roof mechanism in this exposed section of roof mechanism and the sound stopped.
Now I've had the sound stop before so I'm not 100% on this but it appears that it may indeed be roof mechanism related. So, next I will contact BMW to locate what lubrication type is required, get some and apply it to every moving contact surface to see if this helps. If this does not, I'll explore the rubber roof supports and make minor alterations to see if this also helps.
I'll keep this thread updated with findings as I go...
Black Sapphire BMW Z4 sDrive35i
Mods: HiFi Tweeters Stubby LED Halos & Front Indicators DVDInMotion SmartTop 313 BMW Performance Alloys LCI Repeaters http://goo.gl/PF4nSz