Sambucus is a treehouse in a bit of woodland near Finstock. It's modern and quite open inside, with big windows and glass doors. The ceiling has lots of little lights. It gets a lot of sun.
It sleeps four, in two bedrooms. There are two bathrooms, which is handy. It's a 5 Star place, so it's well finished and comfortable. It's up steps, so you need to be okay with that.
There's a wood burner in the main room. You get your own parking space. Bedding and towels are included, and there's wifi. It's one of a few similar properties on the site, so you might see other guests.
You're about half an hour from Oxford. Blenheim Palace is even closer, maybe a 15 minute drive. The Chimney Meadows nature reserve is nearby if you like walking.
For other days out, the National Trust has several properties in the area, like Buscot Park. The Cotswolds are right there too.