Ms Magnus took over the running of Stokesay Court from her aunt in 1995 and said it took her 10 years to renovate it.
The house gained widespread fame when Atonement, starring Keira Knightley and James McAvoy, was shot there and went on to win major awards including an Oscar.
Opening it up to the public had been “fantastic” Ms Magnus said, and had given her the chance to meet lots of people.
But she said when she broke her ankle, she asked herself: “Do I want to do this or do I want to sit and enjoy the house?”
She said she plans to “enjoy it more as a home than a business” from now on and public visits would come to an end at Christmas.