For weddings, the heart of things is the Threshing Barn next to a 17th-century Grade II* listed farmhouse.
The barn and courtyard
The Threshing Barn is where the celebration happens. Right outside, the courtyard has a canopy, so you get indoor space and sheltered outdoor space side by side. Very useful in an English summer. Couples' reviews on the site also talk up the different corners of the grounds for photos.
Because it's open to the public with a café and walks, ask how your wedding is kept private and which parts of the estate you'll have to yourselves. The estate also runs wedding fairs, including a summer one, which is an easy way to look round. If you're a history fan, ask about the archaeology. Guests love a bit of backstory.
Staying on site
Inside the farmhouse there's a two-bedroom self-catering apartment. Couples use it to get ready in the morning and to stay the night, and it's booked through the wedding coordinator as an add-on. The weddings page doesn't say whether ceremonies are licensed on site, so ask about that early if you want everything in one place.
It's worth thinking about where everyone else stays. Wellingborough and Rushden both have hotels nearby, and it's handy to suggest a couple when you send out invitations.
Entertainment that fits
Because the estate is a public heritage site with lots of history, guests often enjoy something with a bit of personality during the drinks. A magician does that. Lewis Joss performs close-up magic and works well under a canopy as much as on a lawn. In the barn in the evening, a photo booth gives you plenty of memories to keep.