With Mr Greville's upcoming retirement, the couple want to downsize so they don't have to spend their time maintaining the gardens.
"You can have nine or 10 guests and hardly ever see them," she said.
"It would be so much better if it was being used for a family."
The couple have made drastic alterations to the outdoor area and gardens - and discovered a glass house, bridge and steps along the way - but much of the original building is intact.
"The couple have added outside doors from the sunroom, and the house also features a butler's pantry, drawing room, the original maid's quarters and the bell system.
Mrs Greville has many wonderful memories of the house and said living on the 8000sq m section was like living in the middle of a park.
She said they know of all the previous owners since it was built in the 1930s and they are hoping to find the right people to take over.
Mrs Greville was sad to be moving but felt incredibly lucky to have had the chance to live there.
It wasn't a million-dollar house when they bought it but it was "the most expensive house sold at the time," she said.
Andy Scott, of Professionals Masterton, said properties worth $1 million seldom came up in residential Masterton.
The only property to sell in Masterton over this price was in Rahiwi Pl, by Deb and Dinah Keats, in 2007.
He believed the valuation of Woodchester was much more than what was being asked.
So what makes it a million-dollar house?
"The age, the era, the style, the square metres ..." he said.
"The grounds alone are of exceptional value and combined with the pristine homestead, this property has a registered valuation which indicates a value well in excess of one million.
"Anyone with the ability to purchase this rare property will very quickly see the value and will appreciate the lifestyle and grandeur of this old lady."