I'd love to visit Sissinghurst, famous for its garden, esp the 'white garden'. People try to reproduce it in NZ but inevitably fail. If we have a white garden with just white flowers it looks to glarey in the NZ light, (it only really comes to life in the nighttime) and well yea, there is only that one castle, Larnach Castle. But the Larnach Castle garden is amazing.
The owner, Mrs Barker, would source plants from South America which has similar climate to Dunedin, as well as our own natives (the iconic Cabbage Trees) and there's a touch of Scottish heather as well. One of the gardens has an Alice in Wonderland Queen of Hearts throne. She also has a laburnum arch which is stunning in flower, and be the side on the slope, a south seas garden full of exotic (to NZ) plants.
Anyway, I don't own a castle, only in my dreams.
Also, have you not read the book 'I capture the castle' by Dodie Smith? Yes most people don't own castles, but then nowadays most people can't even dream of owning their own house anymore.
I mean I don't and I'm an adult.