The Daily Mirror said that some 50 friends and family were expected to attend, including David and Victoria Beckham.
A representative for John declined comment.
John earlier this year said that he and Furnish were planning to marry "very quietly" in the presence of their two children.
The singer voiced pride that England and Wales began allowing same-sex marriage in March. Scotland followed suit this week.
John and Furnish -- who divide their time between England, Atlanta, Venice and Nice in the south of France -- entered a civil partnership soon after the institution began in Britain in 2005.
"I'm very proud of Britain and the laws that we've seen come into existence since we've been together," John told US network NBC in March.
"Having our civil partnership was an incredible breakthrough for people that have campaigned for a long time -- through the '60s and the '50s in England when it was so hard to be gay and hard to be open about it. And it was a criminal act.
"So for this legislation (gay marriage) to come through is joyous, and we should celebrate it. We shouldn't just say, 'Oh, well we have a civil partnership. We're not going to bother to get married.' We will get married," he said.
Early in his career, John was in the closet and married a woman. He later became an advocate for gay rights and has been active in the fight against AIDS.
--------------------------------------------------------------------------------------------------------
A representative for John declined comment.
John earlier this year said that he and Furnish were planning to marry "very quietly" in the presence of their two children.
The singer voiced pride that England and Wales began allowing same-sex marriage in March. Scotland followed suit this week.
John and Furnish -- who divide their time between England, Atlanta, Venice and Nice in the south of France -- entered a civil partnership soon after the institution began in Britain in 2005.
"I'm very proud of Britain and the laws that we've seen come into existence since we've been together," John told US network NBC in March.
"Having our civil partnership was an incredible breakthrough for people that have campaigned for a long time -- through the '60s and the '50s in England when it was so hard to be gay and hard to be open about it. And it was a criminal act.
"So for this legislation (gay marriage) to come through is joyous, and we should celebrate it. We shouldn't just say, 'Oh, well we have a civil partnership. We're not going to bother to get married.' We will get married," he said.
Early in his career, John was in the closet and married a woman. He later became an advocate for gay rights and has been active in the fight against AIDS.
--------------------------------------------------------------------------------------------------------