I smacked on a fresh set of strings, had the intonation set & no longer have an issue with the G String. All 3 x tuners are reading approximately the same thing which is acceptable from what I've read in these forums.
Moral of my story is "don't sit on a set of strings for 6 months waiting for one to break, before changing them over"
Thanks to all who replied to this post, it was from your answers I was able to make the world a better place.
Ball_ed's post in Hd500 Tuner Not Accurate was marked as the answer