I managed to get it all finally working properly with the use of 2x of these:
https://www.amazon.co.uk/AudioPro-A2...tronics&sr=1-1
These are 1:1 transmission isolation transformers that magnetically stop all the pops, whines and unwanted noises whilist maintaining flat frequency response of 20 – 33000Hz (CD's being 20–20,000 Hz which pretty much is the actual human hearing range) which basically means the sound that comes out of the DAC in the head unit is the same unchanged signal that goes into the bose minus the unwanted rubbish.
I also found a newer more up to date ROM for the HU (this voids your warranty etc) which is much quicker and has tonnes of additional features, this is the run down of the menu:
https://www.youtube.com/watch?v=VrRkga1hwLc
I can finally say the installation of this HU into the car is done and if any of you decides to buy it, you just need to get those 2 filters and a 6-7mm 'shim' to stick under the radio (pic attached) to make it sit properly in place of the RNS-D as other wise it will sit at an angle and gaps arround the surround will look dodgy. In my case I used 3 strips of 2mm sound deadning mat.