Hi everyone, thank you for your patience! I just got off the call with MyRepublic technical support and have successfully connected to Roon outside my home 
. I nearly gave up to be honest but I was willing to dive a little deeper into it and you can’t imagine the look on my face!
Anyway how was I able to resolve this? Long story short, I ordered a static IP address from my ISP however it was pointing to the wrong port on my modem. They switched the port (port 1 to port 2) and within seconds Roon Arc was successfully connected to my Nucleus core… fantastic!!
Perhaps a few takeaways from this, and I am pointing at Roon, is that there should have been a step-by-step guide communicated with us i.e.: from a simple port forwarding process to something a lot more complex. It’s funny when I discussed my case with a friend of mine who’s in IT, explained what was the issue and quickly helped me to resolve this so yeah Roon if you’re reading this, congratulations on the roll out of Roon Arc however I’d strongly suggest a better overall communication especially as for some users (like me) encountered something we never expected. We’re not technician nor engineers, some of us just needed better step-by-step guide.
Cheers!