The Swedish group competed against the late Grease star at the Eurovision Song Contest 1974 in Brighton.
The 49-year-old actress announced on Twitter: ‘I now start my own battle with this disease’.
The 20th series of Strictly Come Dancing will return to BBC One later this year with the launch show scheduled to be recorded on 7 September.
The 31-year-old actor will be back as Aaron Dingle to mark 50 years of the rural soap opera.
The Aston-born musician, 73, was joined onstage by members of his rock band Black Sabbath for the explosive performance.
The Black Sabbath rocker told the crowd, "I love you, Birmingham - it's good to be back!"
The British-born singer died ‘peacefully’ at her ranch in Southern California on Monday morning at the age of 73, her husband said.
Actress Olivia Moore, who plays Sandy in the musical, said Monday night’s West End performance had been a ‘mixed bag of emotions’.
After news of her death broke on Monday famous names took to social media to share memories and send condolences to her family.
The hit Regency-era show is up for best drama series and received two nods in the acting categories for its lead stars.
The 63-year-old actor will star in the new BBC One drama Marriage alongside Nicola Walker.
The British-born singer died ‘peacefully’ at her ranch in Southern California on Monday morning, surrounded by family and friends.