On our way back from Gravetye we dropped in to the RHS garden at Wakehurst that is just up the road. They house a big seed bank, collecting plant seeds from around the world to protect and preserve species diversity. There is also a subset of the RHS's botanical gardens there.
The seed bank is an impressive operation, and is well explained in a series of panels. The whole operation is supported by various means, including admission fees and donations. Give generously, or visit often.
The garden itself is dotted with sculptures and other forms of garden art. I rather liked this one with the bear looking out of the tree, and these toadstools. There's a big owl in a tree, too.