We had a guided tour of the gardens with one of the staff - and he took such care to describe things in a very interesting way - he really seemed to pass on his enthusiasm. The views along the river from down at the bottom of the garden are idyllic. If you're luck you might see seals and cormorants - as we did. Take your binoculars!!
Be sure to book your car in to the car park in advance, or go by public transport. See the property's website, or National Trust Handbook.