So thank you all for the feedback.
Big thank you to Dave @OzoneVibe for the reading material on POI and Waypoints. I had a little adjust with the route to take me round the whole of the power station (to keep sort of legal), and added the main chimney as a POI for the route in and out, still needs a little more adjusting and another days flying.
6.8km completed in 13:32 with 44% battery left (for the kids to have a play around the fields). Only dipped slightly on signal at the back of the run (waypoint 5) can be expected there are some pretty big magnetic forces at play in there.
Video again straight from the card, speeded up to 8x to make it a little more interesting.
I look forward to your comments ;o)