The aim is to open the Grade I-listed Tudor building to visitors, with £4.75 million the expected asking price.
The building, which contains two chapels, was home to the Huddleston family, one of the most prominent of Recusant families, and was visited by Mary I on her way to taking the throne.
The campaign by the Sawston Hall Heritage Trust wants the home to be opened to the public, and is backed by leading Catholics including Cardinal Cormac Murphy-O’Connor, the former Archbishop of Westminster and former Conservative MP Ann Widdecombe.
Before the current building was put up a medieval building stood on the site, which is where Queen Mary stayed on her route from Norwich to London to take the throne in 1553.
According to folklore she escaped from the Duke of Northumberland, who had been involved in putting her cousin Lady Jane Grey on the throne, while dressed as a dairymaid, and looked back to see the building in flames, promising to rebuild when she was Queen.
This she did and work finished on the current building in 1584.
During the reign of Elizabeth I Lady Huddleston was summoned to London to explain why she did not attend Anglican services and being ill sent St John Rigby as her representative.
He revealed he was Catholic and was executed.
The Huddlestons owned the house until 1981, after which it became a language school until 2002. It was bought by internet entrepeneur Stephen Coates four years ago, in a state of disrepair, and he has spent millions refurbishing it.
Mr Coates said: “One of the fascinating things about this house is, it was like a castle. It was built with the stone of Cambridge Castle, with a grant from Mary I, and like a lot of these country houses, it was built by exceptionally talented craftsmen, and it took them 27 years.
“It has retained its integrity. One of the reasons is that because of the poverty of the Catholic family they weren’t able to knock it down and rebuild it, as was the case with many grand houses.
“There are three priest holes in the building, including one in the spiral staircase designed by the famous Jesuit Nicholas Owen, who was martyred in 1606.
“He was an extremely clever stonemason, it was designed for someone to hide. He never revealed the locations of these priest holes even when tortured, he was a very special person. The kids have had an incredible time here. There is history everywhere. If you grow up and see that history it’s a tremendous education.”
Mr Coates spent four years refurbishing the house, which did not have a functioning lavatory when they arrived, and at one point 100 people were working on the building. He said the plan was for the centre to act as a social enterprise, including offering affordable loans. He paid tribute to all those who had helped with the project, and encouraged it.
Among these were the late Canon Timothy Russ, a Buckinghamshire priest who inherited the artefacts and furnishings of Sawston Hall from his mother, a Huddleston, and Brian Plunkett, whose brainchild the heritage centre is.
In the 19th century Sawston Hall hosted a number of distinguished visitors, including Daniel O’Connell and Empress Eugénie, the wife of Napoleon III.
Mr Coates said: “That was a motivation. The first time I came here and looked properly. It immediately strikes you that there is an unique combination of religion, military history, the atmosphere is like an abbey, and we are a Christian family. So the religious side is a great asset, it has two chapels. It’s got tremendous religious history.
“The site here is very old, from medieval times there was a history. Then there was obviously the whole phase when Catholicism was struggling and had problems.”
The hall also played a big part in the Second World War as a base for US airmen, and hosted Winston Churchill and General Eisenhower. The hall contains graffiti by US soldiers. After the war Marlon Brando stayed while filming The Nightcomers.
The archives, which are stored at County Hall, Cambridge, go back to the 14th century and include proceedings at the manor court.
The hall’s paintings are held at St Edmund’s College, Cambridge, and include a portrait of the Queen, and the college has offered to return some of the Huddleston’s heirlooms to the building. There is also a portrait of Lord Hardwick who, according to Father Russ, fell in love with a Lady Huddleston but could not marry her because he was not Catholic.
Brian Plunkett, one of the heritage group’s trustees, said: “It’s a magnificent hall which has been beautifully restored. The hall boasts a 100ft great hall, a panelled Queen Anne room, a stunning gallery and a chapel, plus three priest holes.”