I managed to get the cable to where I wanted Jp1i! Once again cheers for the help! My method was a little different, basically I pulled down the rear passenger weather rubbers and also the rubbers from the tailgate to access underneath the headliner. I fed the cable from the rear passenger side headliner using a 400mm cable tie and pulled it out the tailgate side. I used another cable tie of the same length and fed it down the rubber grommet between the vehicle and tailgate, attached the two cable ties together with electrical tape and pulled the cable upwards and there you go! Camera cable is now in the tailgate area! The rest is straightforward from there. It's a little tedious but with a little exploring and planning it actually isnt too hard!
I actually managed to snap 2 out of 4 clips on the tailgate trim beneath the rear stop light as I did not use the right tool, but fixed them with a little super glue!
Hope this makes sense to anyone who else wanting to install the rear camera! Quite happy to also explain further if need be.