We found Lesmahagow on our way around the South Island intending to spend a night and then carry on. We ended up spending two nights with a day exploring the Catlins.
The house itself is gorgeous - an early 1900s building kept in incredible condition. The rooms are huge, with comfortable furniture (including long lounges for tall people to stretch out on!) arrayed through them.
The gardens alone are worth staying here. Perfect grass courtyards for wandering or reading, a huge veggie garden from which Kate gathers a lot of the food for guests...and on that note: take the dinner option. Seriously. Don't go out, don't go anywhere, ask Kate to cook dinner. She clearly enjoys cooking and is incredibly good at it, taking seasonal veggies from the garden and making works of art.
We thought nothing would top the Ferry Hotel B&B outside Queenstown (also highly recommended) but Lesmahagow did it in spades.