I have just added this to the map of places to fly your drone at Drone Scene - Location # 496
Halnaker Windmill is accessed up a long track which is also a public footpath. There is a small parking area on the A285 at the junction with Dredge Lane. As you reach the Windmill you will see that the piece of land it is on is own by West Sussex County Council.
I used the wide public footpath / track on the approach to take off an land ( just out of shot bottom right) as it gives a good view up and down the path and is far enough away from the Windmill not to breach the drone code.
Just a note that this is just outside the Chichester/Goodwood FRZ. There are a lot of small aircraft that use the airfield so you need to be constantly aware or your airspace and the limits of where you can fly.