I had a feeling I was close to the end, and decided to go off doing some exploring (I had an explorer perk which opened all the locations on the map), but was only finding caps and ammo etc, no side missions, so I grew bored and carried on with the story.
Much to my chagrine, I hadnt realised just how close to the end I was, and had to end up finishing the game!

I reached level 20 sometime last week, so there was also no more levelling up options, which made the game lose some of its shine as well!