I am new to the burrow and have been a fan of Watership Down since I was about 10 years old (3 years after the novel came out).
I have visited the real Watership Down and even saw rabbits at the bottom of the hill!
I saw the iron tree and Nuthanger Farm (from the lane) while I was in the neighbourhood too.
I was excited as a kid at Christmas when I discovered the tree above the honeycomb. Wow!
I am currently developing a game for smart phones (iPhone/Android) and tablets based on the scene where Hazel tries to free the hutch rabbits at Nuthanger Farm.
I am currently raising funds for the game here if you'd like to have a look at the game concept:
http://igg.me/p/266039/x/836270