So the new conversion tracking in Unbounce is a PITA
However I have found out a way to get it working. If you follow the most logical instructions, it will not work.
This is the only way I have found to get it working:
Install the Google Site Lag on Main Landing Page only using the script tool.
Put no additional Adwords tracking code on the main landing page.
I hope this helps others who, like me, spent hours trying to get this working.